Merge Dockerfile and example files for backend support example (#7)

* Add template dockerfile for testing

* Switch to holo-docker image

* Add default entrypoint.sh

* Updated dockerfile to reflect CI/CD on database

* Add template makefile, main.c

* Adjusted entrypoint.sh to actually build binary

* Made entrypoint.sh executable

* Big README update and comments in Dockerfile

backend/Dockerfile

@@ -0,0 +1,9 @@
+# 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
+
+# entrypoint.sh should always be located in the backend folder
+ENTRYPOINT [ "/backend/entrypoint.sh" ]

backend/Makefile

@@ -0,0 +1,14 @@
+# This is the default target, which will be built when 
+# you invoke make
+.PHONY: all
+all: hello
+
+# This rule tells make how to build hello from hello.cpp
+hello:
+	mkdir -p ./out
+	gcc -o ./out/hello ./src/main.c 
+
+# This rule tells make to delete hello and hello.o
+.PHONY: clean 
+clean:
+	rm -f hello

backend/entrypoint.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+set -e
+
+echo "Container's IP address: `awk 'END{print $1}' /etc/hosts`"
+
+cd /backend
+
+make

backend/src/main.c

@@ -0,0 +1,5 @@
+#include <stdio.h>
+int main() {
+  printf("Hello World\n");
+  return 0;
+}