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/src/main.c

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