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/android/app/src/main/AndroidManifest.xml

@@ -0,0 +1,34 @@
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.example.context_menus">
+   <application
+        android:label="context_menus"
+        android:name="${applicationName}"
+        android:icon="@mipmap/ic_launcher">
+        <activity
+            android:name=".MainActivity"
+            android:exported="true"
+            android:launchMode="singleTop"
+            android:theme="@style/LaunchTheme"
+            android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
+            android:hardwareAccelerated="true"
+            android:windowSoftInputMode="adjustResize">
+            <!-- Specifies an Android theme to apply to this Activity as soon as
+                 the Android process has started. This theme is visible to the user
+                 while the Flutter UI initializes. After that, this theme continues
+                 to determine the Window background behind the Flutter UI. -->
+            <meta-data
+              android:name="io.flutter.embedding.android.NormalTheme"
+              android:resource="@style/NormalTheme"
+              />
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN"/>
+                <category android:name="android.intent.category.LAUNCHER"/>
+            </intent-filter>
+        </activity>
+        <!-- Don't delete the meta-data below.
+             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
+        <meta-data
+            android:name="flutterEmbedding"
+            android:value="2" />
+    </application>
+</manifest>