Replace tribute with text-expander-element for textarea (#23985)

The completion popup now behaves now much more as expected than before
for the raw textarea:
- You can press <kbd>Tab</kbd> or <kbd>Enter</kbd> once the completion
popup is open to accept the selected item
- The menu does not close automatically when moving the cursor
- When you delete text, previously correct suggestions are shown again
- If you delete all text until the opening char (`@` or `:`) after
applying a suggestion, the popup reappears again
- Menu UI has been improved

<img width="278" alt="Screenshot 2023-04-07 at 19 43 42"
src="https://user-images.githubusercontent.com/115237/230653601-d6517b9f-0988-445e-aa57-5ebfaf5039f3.png">

package-lock.json

@@ -13,6 +13,7 @@
         "@citation-js/plugin-software-formats": "0.6.1",
         "@claviska/jquery-minicolors": "2.3.6",
         "@github/markdown-toolbar-element": "2.1.1",
+        "@github/text-expander-element": "2.3.0",
         "@mcaptcha/vanilla-glue": "0.1.0-alpha-3",
         "@primer/octicons": "18.3.0",
         "@vue/compiler-sfc": "3.2.47",
@@ -840,11 +841,24 @@
         "node": "^12.22.0 || ^14.17.0 || >=16.0.0"
       }
     },
+    "node_modules/@github/combobox-nav": {
+      "version": "2.1.7",
+      "resolved": "https://registry.npmjs.org/@github/combobox-nav/-/combobox-nav-2.1.7.tgz",
+      "integrity": "sha512-Webx0W5iTpkk5Chy9dB/1BEUORQ0qrwui8HaaVBiy75W2VOJg96WTuKj1rXENAJ3XTMhdEF53bn0LYfvP0EKvg=="
+    },
     "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/@github/text-expander-element": {
+      "version": "2.3.0",
+      "resolved": "https://registry.npmjs.org/@github/text-expander-element/-/text-expander-element-2.3.0.tgz",
+      "integrity": "sha512-E1KCxTOA/7Y4dP5g7vXbfRDFU6/SjU0TuJxx6JMwvxzI/NlBrXyXsx/fjFskD2T/un6i6CNKnXu1ZwExDLjcqw==",
+      "dependencies": {
+        "@github/combobox-nav": "^2.0.2"
+      }
+    },
     "node_modules/@humanwhocodes/config-array": {
       "version": "0.11.8",
       "resolved": "https://registry.npmjs.org/@humanwhocodes/config-array/-/config-array-0.11.8.tgz",