feat: add widgets schema validation (#3841)

packages/netlify-cms-widget-map/src/index.js

@@ -1,11 +1,13 @@
 import withMapControl from './withMapControl';
 import previewComponent from './MapPreview';
+import schema from './schema';
 
 const controlComponent = withMapControl();
 const Widget = (opts = {}) => ({
   name: 'map',
   controlComponent,
   previewComponent,
+  schema,
   ...opts,
 });
 

packages/netlify-cms-widget-map/src/schema.js

@@ -0,0 +1,6 @@
+export default {
+  properties: {
+    decimals: { type: 'integer' },
+    type: { type: 'string', enum: ['Point', 'LineString', 'Polygon'] },
+  },
+};