Static fileserver improvements, optional admin panel route (#100)

* better asset serving, optional admin panel route

* linting

internal/router/router.go

@@ -46,6 +46,8 @@ type Router interface {
 	AttachMiddleware(handler gin.HandlerFunc)
 	// Attach 404 NoRoute handler
 	AttachNoRouteHandler(handler gin.HandlerFunc)
+	// Add Gin StaticFile handler
+	AttachStaticFS(relativePath string, fs http.FileSystem)
 	// Start the router
 	Start()
 	// Stop the router
@@ -61,6 +63,11 @@ type router struct {
 	certManager *autocert.Manager
 }
 
+// Add Gin StaticFile handler
+func (r *router) AttachStaticFS(relativePath string, fs http.FileSystem) {
+	r.engine.StaticFS(relativePath, fs)
+}
+
 // Start starts the router nicely.
 //
 // Different ports and handlers will be served depending on whether letsencrypt is enabled or not.