[federated_plugin] adds web implementation of federated_plugin (#507)

experimental/federated_plugin/federated_plugin_platform_interface/pubspec.lock

@@ -7,7 +7,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.4.2"
+    version: "2.4.1"
   boolean_selector:
     dependency: transitive
     description:
@@ -15,13 +15,6 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "2.0.0"
-  characters:
-    dependency: transitive
-    description:
-      name: characters
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.1.0-nullsafety"
   charcode:
     dependency: transitive
     description:
@@ -42,7 +35,7 @@ packages:
       name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.15.0-nullsafety"
+    version: "1.14.12"
   fake_async:
     dependency: transitive
     description:
@@ -66,14 +59,14 @@ packages:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.8"
+    version: "0.12.6"
   meta:
     dependency: transitive
     description:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.3.0-nullsafety"
+    version: "1.1.8"
   path:
     dependency: transitive
     description:
@@ -87,7 +80,7 @@ packages:
       name: pedantic
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.2"
+    version: "1.9.0"
   plugin_platform_interface:
     dependency: "direct main"
     description:
@@ -113,7 +106,7 @@ packages:
       name: stack_trace
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.5"
+    version: "1.9.3"
   stream_channel:
     dependency: transitive
     description:
@@ -141,21 +134,21 @@ packages:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.17"
+    version: "0.2.16"
   typed_data:
     dependency: transitive
     description:
       name: typed_data
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.3.0-nullsafety"
+    version: "1.1.6"
   vector_math:
     dependency: transitive
     description:
       name: vector_math
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.0-nullsafety"
+    version: "2.0.8"
 sdks:
-  dart: ">=2.9.0-18.0 <2.9.0"
+  dart: ">=2.7.0 <3.0.0"
   flutter: ">=1.17.0 <2.0.0"

experimental/federated_plugin/federated_plugin_platform_interface/pubspec.yaml

@@ -1,5 +1,5 @@
 name: federated_plugin_platform_interface
-description: A new Flutter package project.
+description: A platform interface for federated_plugin.
 version: 0.0.1
 author:
 homepage: