Show/document quick and dirty, bare-bones (for debug/learning...) Dockerized WebPageTest (+agent) setup

Essentially:

• Start our Dockerized WebPageTest (PHP) server instance (API + Web UI):

docker run --rm -d -p 4001:80 webpagetest/server

• Start a Dockerized wptagent agent:

  docker run --rm -d \
  --network="host" \
  -e vvvv
  -e SERVER_URL=http://localhost:4001/work/ \
  -e LOCATION="Test" \
  -e SHAPER="none" \
  --cap-add=NET_ADMIN \
  webpagetest/agent

Once installed, check http://localhost:4001/install/ for the installation checklist.