Introduce GitHub markdown editor, keep EasyMDE as fallback (#23876)

The first step of the plan

* #23290

Thanks to @silverwind for the first try in #15394 . Close #10729 and a
lot of related issues.

The EasyMDE is not removed, now it works as a fallback, users can switch
between these two editors.

Editor list:

* Issue / PR comment
* Issue / PR comment edit
* Issue / PR comment quote reply
* PR diff view, inline comment
* PR diff view, inline comment edit
* PR diff view, inline comment quote reply
* Release editor
* Wiki editor

Some editors have attached dropzone

Screenshots:

<details>


![image](https://user-images.githubusercontent.com/2114189/229363558-7e44dcd4-fb6d-48a0-92f8-bd12f57bb0a0.png)


![image](https://user-images.githubusercontent.com/2114189/229363566-781489c8-5306-4347-9714-d71af5d5b0b1.png)


![image](https://user-images.githubusercontent.com/2114189/229363771-1717bf5c-0f2a-4fc2-ba84-4f5b2a343a11.png)


![image](https://user-images.githubusercontent.com/2114189/229363793-ad362d0f-a045-47bd-8f9d-05a9a842bb39.png)

</details>

---------

Co-authored-by: silverwind <me@silverwind.io>

package-lock.json

@@ -12,6 +12,7 @@
         "@citation-js/plugin-csl": "0.6.7",
         "@citation-js/plugin-software-formats": "0.6.1",
         "@claviska/jquery-minicolors": "2.3.6",
+        "@github/markdown-toolbar-element": "2.1.1",
         "@mcaptcha/vanilla-glue": "0.1.0-alpha-3",
         "@primer/octicons": "18.3.0",
         "@vue/compiler-sfc": "3.2.47",
@@ -838,6 +839,11 @@
         "node": "^12.22.0 || ^14.17.0 || >=16.0.0"
       }
     },
+    "node_modules/@github/markdown-toolbar-element": {
+      "version": "2.1.1",
+      "resolved": "https://registry.npmjs.org/@github/markdown-toolbar-element/-/markdown-toolbar-element-2.1.1.tgz",
+      "integrity": "sha512-J++rpd5H9baztabJQB82h26jtueOeBRSTqetk9Cri+Lj/s28ndu6Tovn0uHQaOKtBWDobFunk9b5pP5vcqt7cA=="
+    },
     "node_modules/@humanwhocodes/config-array": {
       "version": "0.11.8",
       "resolved": "https://registry.npmjs.org/@humanwhocodes/config-array/-/config-array-0.11.8.tgz",