Initial action stub

Now that I know how to write some simple action, let's make a stub
more complete. For example, I already know what inputs I would like
to handle for this action.

index.js

@@ -0,0 +1,6 @@
+const core = require('@actions/core')
+
+async function main() {
+}
+
+main().catch(() => core.setFailed('could not setup Developer Command Prompt'))