Make a skeleton repo to allow building scripted checks locally

[rdubrock]

There are some cases which require writing scripted checks locally, specifically if you want to bundle node modules in with your script.

We should make a skeleton repo that shows how to set up webpack to bundle dependencies with the check, test them with the k6 cli, and the upload them either via the SM api go client or terraform

[rdubrock]

This is now mostly done with https://github.com/grafana/synthetics-example-app

The terraform provider needs to have scripted support added, which is happening via https://github.com/grafana/terraform-provider-grafana/pull/1456

After that the repo needs to be made public, and added to documentation where appropriate