[file_selector] Endorse web (flutter#3643)

Author: stuartmorgan-g

packages/file_selector/file_selector/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.8.1
+
+Endorse the web implementation.
+
 ## 0.8.0
 
 Migrate to null safety.

packages/file_selector/file_selector/pubspec.yaml

@@ -1,12 +1,19 @@
 name: file_selector
 description: Flutter plugin for opening and saving files.
 homepage: https://github.com/flutter/plugins/tree/master/packages/file_selector/file_selector
-version: 0.8.0
+version: 0.8.1
+
+flutter:
+  plugin:
+    platforms:
+      web:
+        default_package: file_selector_web
 
 dependencies:
   flutter:
     sdk: flutter
   file_selector_platform_interface: ^2.0.0
+  file_selector_web: ^0.8.1
 
 dev_dependencies:
   flutter_test: