Added ExtendsClass to list of Validators

Adds ExtendsClass's JSON Schema Validator to list of Online Validators.
And adds draft-07 for JSON Schema Lint.

Author: cyrilbois

_data/validator-libraries-modern.yml

@@ -134,7 +134,10 @@
       draft: [7, 6, 4, 3]
     - name: JSON Schema Lint
       url: http://jsonschemalint.com/
-      draft: [6, 4, 3, 2, 1]
+      draft: [7, 6, 4, 3, 2, 1]
+    - name: ExtendsClass's JSON Schema Validator
+      url: https://extendsclass.com/json-schema-validator.html
+      draft: [7]
 - name: Command Line
   implementations:
     - name: ajv-cli