Update url-strings-and-tokens-in-sharepoint-add-ins.md (SharePoint#4451)

The table formatting was messed up in docs.microsoft.com even though in github it looked ok in preview.
added some line breaks to try to get the table formatting to show correctly. I did see the comment after the first table was getting appended to the table, and this likely was the cause of the table formatting problem in Docs.

Author: westleyMS

docs/sp-add-ins/url-strings-and-tokens-in-sharepoint-add-ins.md

@@ -23,6 +23,8 @@ In each table:
 - The **Custom Action** column specifies whether the token can be used in the URL of a custom action on a host web. 
 - The **Add-in Part** column specifies whether the token can be used in the **Src** property of the add-in part.
 
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 ## Tokens that you can use at the beginning of a URL
 
 |**Token**|**Resolves to**|**StartPage**|**Custom Action**|**Add-in Part**|**Remarks**|
@@ -35,6 +37,7 @@ In each table:
 |~remoteAppUrl|The URL of a remote web application in a SharePoint Add-in.|Yes|Yes, in the host web, but No in the add-in web.|Yes|If you are not using Microsoft Office Developer Tools for Visual Studio to develop your SharePoint Add-in, you cannot use **~remoteAppUrl** in the **StartPage** URL. However, when you are using Visual Studio and the tools, you can use this token for any provider-hosted add-in and it is resolved when Visual Studio packages the add-in. In this usage, it is really more of a Visual Studio token than a SharePoint token. It can be used outside the add-in manifest, even when you are not using Microsoft Office Developer Tools for Visual Studio.|
 |~site|The URL of the current website.|No|No|Yes||
 |~sitecollection|The URL of the parent site collection of the current website.|No|No|Yes||
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 Except where indicated otherwise, none of the tokens in the next table can be used in the  *path*  portion of the **Src** property value of the add-in part. The **Add-in Part** column refers to their use in the *query string*  portion of the value.