Align type field for $self with style guide.

Also tweak the wording a bit as a result, and ran format-markdown.

Author: handrews

src/oas.md

@@ -367,9 +367,9 @@ components:
       $id: ./schemas/bar
 ```
 
-In this example, both Schema Objects use `https://example.com/openapi` as their base URI for resolving their relative `$id` values to `https://example.com/schemas/foo` and `https://example.com/schemas/bar`.  The `$ref` under `properties` is resolved against the `$id`-provided base URI `https://example.com/schemas/foo`, producing `https://example.com/schemas/bar`, which is the `$id`-assigned URI of the Bar schema component.
+In this example, both Schema Objects use `https://example.com/openapi` as their base URI for resolving their relative `$id` values to `https://example.com/schemas/foo` and `https://example.com/schemas/bar`. The `$ref` under `properties` is resolved against the `$id`-provided base URI `https://example.com/schemas/foo`, producing `https://example.com/schemas/bar`, which is the `$id`-assigned URI of the Bar schema component.
 
-Note that using embedded `$id` keywords would prevent using `$ref: "#/components/schemas/Bar"` in the `properties` keyword's `$ref` because the base URI for such fragments is set by the `$id`.  Therefore, a `$ref: "#/components/schemas/Bar"` would resolve to `"https://example.com/schemas/foo#/components/schemas/Bar"`, rather than the presumably-intended ___location of `"https://example.com/openapi#/components/schemas/Bar"`.
+Note that using embedded `$id` keywords would prevent using `$ref: "#/components/schemas/Bar"` in the `properties` keyword's `$ref` because the base URI for such fragments is set by the `$id`. Therefore, a `$ref: "#/components/schemas/Bar"` would resolve to `"https://example.com/schemas/foo#/components/schemas/Bar"`, rather than the presumably-intended ___location of `"https://example.com/openapi#/components/schemas/Bar"`.
 
 #### Resolving URI fragments
 
@@ -402,7 +402,7 @@ servers:
   description: The test API on this device
 ```
 
-For API URLs, the `$self` field, which identifies the OpenAPI Document, is ignored, and the retrieval URL is used instead.  This produces a normalized production URL of `https://device1.example.com`, and a normalized test URL of `https://device1.example.com/test`.
+For API URLs, the `$self` field, which identifies the OpenAPI Document, is ignored, and the retrieval URL is used instead. This produces a normalized production URL of `https://device1.example.com`, and a normalized test URL of `https://device1.example.com/test`.
 
 ### Schema
 
@@ -422,7 +422,7 @@ This is the root object of the [OpenAPI Description](#openapi-description).
 | Field Name | Type | Description |
 | ---- | :----: | ---- |
 | <a name="oas-version"></a>openapi | `string` | **REQUIRED**. This string MUST be the [version number](#versions) of the OpenAPI Specification that the OpenAPI Document uses. The `openapi` field SHOULD be used by tooling to interpret the OpenAPI Document. This is _not_ related to the API [`info.version`](#info-version) string. |
-| <a name="oas-self"></a>$self | `URI-reference` (without a fragment) | Sets the URI of this document, which also serves as its base URI in accordance with [[RFC3986]] [Section 5.1.1](https://www.rfc-editor.org/rfc/rfc3986#section-5.1.1); the value MUST NOT be the empty string and MUST NOT contain a fragment (even if the fragment is empty).  Implementations MUST support identifying the targets of [API description URIs](#relative-references-in-api-description-uris) using the resolved URI defined by this field, as shown under [Examples of Base URI Determination and Reference Resolution](#examples-of-base-uri-determination-and-reference-resolution).|
+| <a name="oas-self"></a>$self | `string` | This string MUST be in the form of a URI-reference, MUST NOT be an empty string, and MUST NOT contain a fragment (empty or otherwise). The `$self` field provides the self-assigned URI of this document, which also serves as its base URI in accordance with [[RFC3986]] [Section 5.1.1](https://www.rfc-editor.org/rfc/rfc3986#section-5.1.1). Implementations MUST support identifying the targets of [API description URIs](#relative-references-in-api-description-uris) using the resolved URI defined by this field, as shown under [Examples of Base URI Determination and Reference Resolution](#examples-of-base-uri-determination-and-reference-resolution). |
 | <a name="oas-info"></a>info | [Info Object](#info-object) | **REQUIRED**. Provides metadata about the API. The metadata MAY be used by tooling as required. |
 | <a name="oas-json-schema-dialect"></a> jsonSchemaDialect | `string` | The default value for the `$schema` keyword within [Schema Objects](#schema-object) contained within this OAS document. This MUST be in the form of a URI. |
 | <a name="oas-servers"></a>servers | [[Server Object](#server-object)] | An array of Server Objects, which provide connectivity information to a target server. If the `servers` field is not provided, or is an empty array, the default value would be a [Server Object](#server-object) with a [url](#server-url) value of `/`. |
@@ -556,7 +556,7 @@ An object representing a Server.
 
 | Field Name | Type | Description |
 | ---- | :----: | ---- |
-| <a name="server-url"></a>url | `string` | **REQUIRED**. A URL to the target host. This URL supports Server Variables and MAY be relative, to indicate that the host ___location is relative to the ___location where the document containing the Server Object is being served. Variable substitutions will be made when a variable is named in `{`braces`}`.   Note that the [OpenAPI Object's](#openapi-object) `$self` field is **NOT** used for relative URL reference resolution. |
+| <a name="server-url"></a>url | `string` | **REQUIRED**. A URL to the target host. This URL supports Server Variables and MAY be relative, to indicate that the host ___location is relative to the ___location where the document containing the Server Object is being served. Variable substitutions will be made when a variable is named in `{`braces`}`. Note that the [OpenAPI Object's](#openapi-object) `$self` field is **NOT** used for relative URL reference resolution. |
 | <a name="server-description"></a>description | `string` | An optional string describing the host designated by the URL. [CommonMark syntax](https://spec.commonmark.org/) MAY be used for rich text representation. |
 | <a name="server-name"></a>name | `string` | An optional unique string to refer to the host designated by the URL. |
 | <a name="server-variables"></a>variables | Map[`string`, [Server Variable Object](#server-variable-object)] | A map between a variable name and its value. The value is used for substitution in the server's URL template. |