Direct SVG rendering (#12157)

Introduce 'make svg' which calls a node script that compiles svg files
to `public/img/svg`. These files are vendored to not create a dependency
on Node for the backend build.

On the frontend side, configure webpack using `raw-loader` so SVGs can
be imported as string.

Also moved our existing SVGs to web_src/svg for consistency.

Fixes: https://github.com/go-gitea/gitea/issues/11618

web_src/js/index.js

@@ -3555,12 +3555,3 @@ window.onOAuthLoginClick = function () {
     oauthNav.show();
   }, 5000);
 };
-
-// Pull SVGs via AJAX to workaround CORS issues with <use> tags
-// https://css-tricks.com/ajaxing-svg-sprite/
-$.get(`${window.config.StaticUrlPrefix}/img/svg/icons.svg`, (data) => {
-  const div = document.createElement('div');
-  div.style.display = 'none';
-  div.innerHTML = new XMLSerializer().serializeToString(data.documentElement);
-  document.body.insertBefore(div, document.body.childNodes[0]);
-});