Add docs and tests

scripts/create-cache-files.sh

@@ -0,0 +1,17 @@
+#!/bin/sh
+
+# Validate args
+prefix="$1"
+if [ -z "$prefix" ]; then
+  echo "Must supply prefix argument"
+  exit 1
+fi
+
+path="$2"
+if [ -z "$path" ]; then
+  echo "Must supply path argument"
+  exit 1
+fi
+
+mkdir -p $path
+echo "$prefix $GITHUB_RUN_ID" > $path/test-file.txt