ref: move PureWidget back to core, use updateEnv

src/index.ts

@@ -1,6 +1,13 @@
 import { QWeb } from "./qweb";
 import { EventBus } from "./event_bus";
-import { Component } from "./component";
+import { Component, PureComponent } from "./component";
 import { Store, StoreMixin } from "./store";
 
-export const core = { QWeb, EventBus, Component, Store, StoreMixin };
+export const core = {
+  QWeb,
+  EventBus,
+  Component,
+  PureComponent,
+  Store,
+  StoreMixin
+};