Add template dockerfile for testing

backend/Dockerfile

@@ -1,9 +1,6 @@
-# we support images for building with a vanilla SteamOS base,
-# or versions with ootb support for rust or go
-# developers can also customize these images via this Dockerfile
-#FROM ghcr.io/steamdeckhomebrew/holo-toolchain-rust:latest
-#FROM ghcr.io/steamdeckhomebrew/holo-toolchain-go:latest
-FROM ghcr.io/steamdeckhomebrew/holo-base:latest
+FROM arch:latest
 
-# entrypoint.sh should always be located in the backend folder
-ENTRYPOINT [ "/backend/entrypoint.sh" ]
+ADD ./backend/ /source
+ADD ./build/backend /build
+
+WORKDIR /source