[ADD] router: initial implementation

src/index.ts

@@ -10,10 +10,13 @@ import { QWeb } from "./qweb/index";
 import { ConnectedComponent } from "./store/connected_component";
 import { Store } from "./store/store";
 import * as _utils from "./utils";
+import { Link } from "./router/Link";
+import { activate } from "./router/plugin";
 
 export { Component } from "./component/component";
 export { QWeb };
 export const core = { EventBus, Observer };
+export const router = { activate, Link };
 export const store = { Store, ConnectedComponent };
 export const utils = _utils;