feat(base/flags): add warning for unsupported feature flags

react/features/base/flags/actions.ts

@@ -1,4 +1,7 @@
+import logger from '../app/logger';
+
 import { UPDATE_FLAGS } from './actionTypes';
+import * as featureFlags from './constants';
 
 /**
  * Updates the current features flags with the given ones. They will be merged.
@@ -10,6 +13,13 @@ import { UPDATE_FLAGS } from './actionTypes';
  * }}
  */
 export function updateFlags(flags: Object) {
+    const supportedFlags = Object.values(featureFlags);
+    const unsupportedFlags = Object.keys(flags).filter(flag => !supportedFlags.includes(flag as any));
+
+    if (unsupportedFlags.length > 0) {
+        logger.warn(`The following feature flags are not supported: ${unsupportedFlags.join(', ')}.`);
+    }
+
     return {
         type: UPDATE_FLAGS,
         flags