Polyfill the window.customElements (#23592)

Related: #23590

Reference:
https://github.com/webcomponents/polyfills/tree/master/packages/webcomponentsjs

It seems that there are some users using old browsers, so the
`window.customElements` need polyfill.

The Custom Elements would help a lot for Gitea's UI problems, including:

* `<span class="js-pretty-number">`
* `<time data-format>`

So it's worth get polyfill.

---------

Co-authored-by: delvh <[email protected]>

Author: wxiaoguang

package-lock.json

@@ -15,6 +15,7 @@
     "@mcaptcha/vanilla-glue": "0.1.0-alpha-3",
     "@primer/octicons": "18.2.0",
     "@vue/compiler-sfc": "3.2.47",
+    "@webcomponents/custom-elements": "1.5.1",
     "add-asset-webpack-plugin": "2.0.1",
     "ansi-to-html": "0.7.2",
     "asciinema-player": "3.2.0",

package.json

@@ -1,3 +1,5 @@
+import '@webcomponents/custom-elements'; // automatically adds custom elements for older browsers that don't support it
+
 // this is a Gitea's private HTML component, it converts an absolute or relative URL to an absolute URL with the current origin
 window.customElements.define('gitea-origin-url', class extends HTMLElement {
   connectedCallback() {