Updated Json Schema which includes cache property (#2011)

## Why this change?

This change follows up on
#1865, which adds caching
support.
VSCode suggesting the new `cache` properties were errors when included
in the config file. That is because the properties needed to be added to
the json schema.

Global `cache` property in the `runtime` section which adjacent to
`rest`, `graphql`, and `host`.

```json
{
  "runtime": {
    "cache": {
      "enabled": false,
      "ttl-seconds": 5
    }
  }
}
```

and per entity alongside `source`, `graphql`, `rest`, and `permissions`

```json
{
  "myEntity": {
    "cache": {
      "enabled": false,
      "ttl-seconds": 5
    }
  }
}
```

Author: seantleonard

schemas/dab.draft.schema.json

@@ -236,6 +236,22 @@
               }
             }
           }
+        },
+        "cache": {
+          "type": "object",
+          "additionalProperties": false,
+          "properties": {
+            "enabled": {
+              "type": "boolean",
+              "description": "Enable caching of responses globally.",
+              "default": false
+            },
+            "ttl-seconds": {
+              "type": "integer",
+              "description": "Time to live in seconds",
+              "default": 5
+            }
+          }
         }
       }
     },
@@ -465,6 +481,22 @@
                   ]
                 }
               }
+            },
+            "cache": {
+              "type": "object",
+              "additionalProperties": false,
+              "properties": {
+                "enabled": {
+                  "type": "boolean",
+                  "description": "Enable caching of responses for this entity.",
+                  "default": false
+                },
+                "ttl-seconds": {
+                  "type": "integer",
+                  "description": "Time to live in seconds",
+                  "default": 5
+                }
+              }
             }
           },
           "if": {