add entrypoint script to action

actions/action.yml

@@ -4,4 +4,4 @@ description: 'Build a document using texlive'
 runs:
   using: 'docker'
   image: 'docker://ghcr.io/mszep/pandoc_resume/resume_builder:latest'
-  entrypoint: [sh, -c, make, pdf]
+  entrypoint: 'entrypoint.sh'

actions/entrypoint.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+make pdf