docs(core): add usage information to AddRoute action

npm/ng-packs/packages/core/src/lib/actions/config.actions.ts

@@ -9,6 +9,9 @@ export class GetAppConfiguration {
   static readonly type = '[Config] Get App Configuration';
 }
 
+/**
+ * @see usage: https://github.com/abpframework/abp/pull/2425#issue-355018812
+ */
 export class AddRoute {
   static readonly type = '[Config] Add Route';
   constructor(public payload: Omit<ABP.Route, 'children'>) {}