Improve context menu looks and behavior

Ref: canonical#72

lib/home/home_menu.dart

@@ -1,3 +1,4 @@
+import 'package:context_menu/context_menu.dart';
 import 'package:flutter/material.dart';
 import 'package:terminal_view/terminal_view.dart';
 
@@ -9,27 +10,27 @@ List<PopupMenuEntry> buildContextMenu({
   required VoidCallback? onCloseTab,
 }) {
   return <PopupMenuEntry>[
-    PopupMenuItem(
+    ContextMenuItem(
       onTap: onNewTab,
       child: const Text('New Tab'),
     ),
-    PopupMenuItem(
+    ContextMenuItem(
       onTap: onCloseTab,
       enabled: tabCount > 1,
       child: const Text('Close Tab'),
     ),
     const PopupMenuDivider(),
-    PopupMenuItem(
+    ContextMenuItem(
       onTap: current?.copy,
       enabled: current?.selectedText?.isNotEmpty == true,
       child: const Text('Copy'),
     ),
-    PopupMenuItem(
+    ContextMenuItem(
       onTap: current?.paste,
       enabled: current != null,
       child: const Text('Paste'),
     ),
-    PopupMenuItem(
+    ContextMenuItem(
       onTap: current?.selectAll,
       enabled: current != null,
       child: const Text('Select All'),

lib/home/home_page.dart

@@ -1,5 +1,6 @@
 import 'dart:async';
 
+import 'package:context_menu/context_menu.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:lxd_service/lxd_service.dart';
@@ -10,7 +11,6 @@ import 'package:ubuntu_service/ubuntu_service.dart';
 import '../instances/instance_view.dart';
 import '../launcher/launcher_wizard.dart';
 import '../terminal/terminal_page.dart';
-import '../widgets/context_menu.dart';
 import 'home_menu.dart';
 import 'home_model.dart';
 

packages/context_menu/.gitignore

@@ -0,0 +1,30 @@
+# Miscellaneous
+*.class
+*.log
+*.pyc
+*.swp
+.DS_Store
+.atom/
+.buildlog/
+.history
+.svn/
+migrate_working_dir/
+
+# IntelliJ related
+*.iml
+*.ipr
+*.iws
+.idea/
+
+# The .vscode folder contains launch configuration and tasks you configure in
+# VS Code which you may wish to be included in version control, so this line
+# is commented out by default.
+#.vscode/
+
+# Flutter/Dart/Pub related
+# Libraries should not include pubspec.lock, per https://dart.dev/guides/libraries/private-files#pubspeclock.
+/pubspec.lock
+**/doc/api/
+.dart_tool/
+.packages
+build/

packages/context_menu/.metadata

@@ -0,0 +1,10 @@
+# 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 and should not be manually edited.
+
+version:
+  revision: ffccd96b62ee8cec7740dab303538c5fc26ac543
+  channel: stable
+
+project_type: package

packages/context_menu/LICENSE

@@ -0,0 +1,25 @@
+Copyright 2014 The Flutter Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+    * Neither the name of Google Inc. nor the names of its
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

packages/context_menu/lib/context_menu.dart

@@ -0,0 +1,3 @@
+library context_menu;
+
+export 'src/context_menu.dart';