Custom context menu example (#1463)

* flutter create

* Copied in from 'contextual-menu-examples' repo

* Works again with the latest updates to the branch

* Clean up anywhere example

* Clean up other examples

* Add to CI

* Updated with release version of context menus, and added platform switcher

* Generated files

* Home icon on your original platform

* Remove web_dashboard from ci, not sure why that change was there...

* Add context_menu to beta channel, but commented out, for the future

* +x permissions on the master script, which I may have accidentally changed before?

* Actual bash comment

* dart format

* Natural default platform'

* A working test, for the email page

* Import order fix

* Test some pages

* More tests

* dart format

experimental/context_menus/.metadata

@@ -0,0 +1,45 @@
+# This file tracks properties of this Flutter project.
+# Used by Flutter tool to assess capabilities and perform upgrades etc.
+#
+# This file should be version controlled.
+
+version:
+  revision: d2434a2b6008698a6d805fce87b310098465bf4c
+  channel: unknown
+
+project_type: app
+
+# Tracks metadata for the flutter migrate command
+migration:
+  platforms:
+    - platform: root
+      create_revision: d2434a2b6008698a6d805fce87b310098465bf4c
+      base_revision: d2434a2b6008698a6d805fce87b310098465bf4c
+    - platform: android
+      create_revision: d2434a2b6008698a6d805fce87b310098465bf4c
+      base_revision: d2434a2b6008698a6d805fce87b310098465bf4c
+    - platform: ios
+      create_revision: d2434a2b6008698a6d805fce87b310098465bf4c
+      base_revision: d2434a2b6008698a6d805fce87b310098465bf4c
+    - platform: linux
+      create_revision: d2434a2b6008698a6d805fce87b310098465bf4c
+      base_revision: d2434a2b6008698a6d805fce87b310098465bf4c
+    - platform: macos
+      create_revision: d2434a2b6008698a6d805fce87b310098465bf4c
+      base_revision: d2434a2b6008698a6d805fce87b310098465bf4c
+    - platform: web
+      create_revision: d2434a2b6008698a6d805fce87b310098465bf4c
+      base_revision: d2434a2b6008698a6d805fce87b310098465bf4c
+    - platform: windows
+      create_revision: d2434a2b6008698a6d805fce87b310098465bf4c
+      base_revision: d2434a2b6008698a6d805fce87b310098465bf4c
+
+  # User provided section
+
+  # List of Local paths (relative to this file) that should be
+  # ignored by the migrate tool.
+  #
+  # Files that are not part of the templates will be ignored by default.
+  unmanaged_files:
+    - 'lib/main.dart'
+    - 'ios/Runner.xcodeproj/project.pbxproj'