Validation: Add "propertyNames" keyword

Author: awwright

Diff for: jsonschema-validation.xml

@@ -550,6 +550,20 @@
                 </t>
             </section>
 
+            <section title="propertyNames">
+                <t>
+                    The value of "properties" MUST be a valid JSON Schema.
+                </t>
+                <t>
+                    If the instance is an object, this keyword validates if every property name in the instance
+                    validates against the provided schema.
+                    Note the property name that the schema is testing will always be a string.
+                </t>
+                <t>
+                    A missing keyword is the same as an empty schema, or a schema testing that the type is "string".
+                </t>
+            </section>
+
             <section title="enum">
                 <t>
                     The value of this keyword MUST be an array. This array SHOULD have at

Diff for: schema.json

@@ -124,6 +124,7 @@
                 ]
             }
         },
+        "propertyNames": { "$ref": "#" },
         "const": {},
         "enum": {
             "type": "array",