Added Basic contextMenus sample (#859)

* Added Basic contextMenus sample

* Updated license header

* Update sample.js

* Update api-samples/contextMenus/basic/sample.js

Co-authored-by: Oliver Dunk <oliverdunk@google.com>

* Update api-samples/contextMenus/basic/sample.js

Co-authored-by: Oliver Dunk <oliverdunk@google.com>

* Update sample.js

* Update sample.js

* Create README.md

* Update api-samples/contextMenus/basic/README.md

Co-authored-by: Oliver Dunk <oliverdunk@google.com>

---------

Co-authored-by: Oliver Dunk <oliverdunk@google.com>

api-samples/contextMenus/basic/README.md

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+# chrome.contextMenus
+
+A sample extension demonstrating use of the chrome.contextMenus API.
+
+## Overview
+
+In this sample the chrome.contextMenus API is used to create menu items, listen for different context menu types being clicked, and run code based on what the user has selected.
+
+## Implementation Notes
+
+Different console readouts are made when context menu items are clicked. This can be quickly adapted to use new functions or API calls for more advaced functionality.

api-samples/contextMenus/basic/manifest.json

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+{
+  "name": "Context Menus Sample",
+  "description": "Shows some of the features of the Context Menus API",
+  "version": "0.7",
+  "permissions": ["contextMenus"],
+  "background": {
+    "service_worker": "sample.js"    
+  },
+  "manifest_version": 3
+}

api-samples/contextMenus/basic/sample.js

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+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// A generic onclick callback function.
+chrome.contextMenus.onClicked.addListener(genericOnClick);
+
+// A generic onclick callback function.
+function genericOnClick(info, tab) {
+  switch (info.menuItemId) {
+    case 'radio':
+      // Radio item function
+      console.log('Radio item clicked. Status:', info.checked);
+      break;
+    case 'checkbox':
+      // Checkbox item function
+      console.log('Checkbox item clicked. Status:', info.checked);
+      break;
+    default:
+      // Standard context menu item function
+      console.log('Standard context menu item clicked.');
+  }
+}
+chrome.runtime.onInstalled.addListener(function () {
+  // Create one test item for each context type.
+  let contexts = [
+    'page',
+    'selection',
+    'link',
+    'editable',
+    'image',
+    'video',
+    'audio'
+  ];
+  for (let i = 0; i < contexts.length; i++) {
+    let context = contexts[i];
+    let title = "Test '" + context + "' menu item";
+    let id = chrome.contextMenus.create({
+      title: title,
+      contexts: [context],
+      id: context
+    });
+  }
+
+  // Create a parent item and two children.
+  let parent = chrome.contextMenus.create({
+    title: 'Test parent item',
+    id: 'parent'
+  });
+  let child1 = chrome.contextMenus.create({
+    title: 'Child 1',
+    parentId: parent,
+    id: 'child1'
+  });
+  let child2 = chrome.contextMenus.create({
+    title: 'Child 2',
+    parentId: parent,
+    id: 'child2'
+  });
+
+  // Create a radio item.
+  let radio1 = chrome.contextMenus.create({
+    title: 'radio',
+    type: 'radio',
+    id: 'radio'
+  });
+
+  // Create a checkbox item.
+  let checkbox1 = chrome.contextMenus.create({
+    title: 'checkbox',
+    type: 'checkbox',
+    id: 'checkbox'
+  });
+
+  // Intentionally create an invalid item, to show off error checking in the
+  // create callback.
+  chrome.contextMenus.create(
+    { title: 'Oops', parentId: 999, id: 'errorItem' },
+    function () {
+      if (chrome.runtime.lastError) {
+        console.log('Got expected error: ' + chrome.runtime.lastError.message);
+      }
+    }
+  );
+});