Add github test case

tests/githubtest/customContent/test.txt

@@ -0,0 +1,3 @@
+Hello world
+
+This is an integration test

tests/githubtest/test.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+set -e
+if [[ -z "$GITHUB_TOKEN" ]]; then
+    echo "ERROR: GITHUB_TOKEN not set (see https://github.com/settings/tokens/new?scopes=write:packages for running locally)"
+    exit 1
+fi
+
+printf "* Running containerify to pull from and push result to the local containerify test registry...\n"
+../../lib/cli.js --verbose --fromImage docker-mirror/node:alpine --registry https://ghcr.io/v2/ --toImage eoftedal/containerify-integrationtest:latest --folder . --customContent customContent --setTimeStamp "2024-01-15T20:00:00.000Z" --token "$GITHUB_TOKEN"