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

modules/svg/discover_bindata.go

@@ -0,0 +1,32 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+// +build bindata
+
+package svg
+
+import (
+	"path"
+	"path/filepath"
+
+	"code.gitea.io/gitea/modules/public"
+)
+
+// Discover returns a map of discovered SVG icons in bindata
+func Discover() map[string]string {
+	svgs := make(map[string]string)
+
+	for _, file := range public.AssetNames() {
+		matched, _ := filepath.Match("img/svg/*.svg", file)
+		if matched {
+			content, err := public.Asset(file)
+			if err == nil {
+				filename := path.Base(file)
+				svgs[filename[:len(filename)-4]] = string(content)
+			}
+		}
+	}
+
+	return svgs
+}