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/utils.js

@@ -1,8 +1,3 @@
-// retrieve a HTML string for given SVG icon name and size in pixels
-export function svg(name, size) {
-  return `<svg class="svg ${name}" width="${size}" height="${size}" aria-hidden="true"><use xlink:href="#${name}"/></svg>`;
-}
-
 // transform /path/to/file.ext to file.ext
 export function basename(path = '') {
   return path ? path.replace(/^.*\//, '') : '';