feat share: Ability to share files using Web Activities

feat pick: Ability to pick files for other apps

src/js/actions/pick.js

@@ -0,0 +1,15 @@
+import { PICK } from 'actions/types';
+
+export function enable(request) {
+  return {
+    type: PICK,
+    active: request
+  }
+}
+
+export function disable() {
+  return {
+    type: PICK,
+    active: false
+  }
+}