feat: add entrypoint script

Dockerfile

@@ -1 +1,5 @@
 FROM kopia/kopia 
+
+ADD entrypoint.sh  / 
+
+ENTRYPOINT [ "/entrypoint.sh" ]

entrypoint.sh

@@ -0,0 +1,4 @@
+#!/bin/sh 
+
+kopia --version
+sleep infinity