This commit implements a fully-automated development setup using Gitpod.io, an
online IDE for GitLab, GitHub, and Bitbucket that enables Dev-Environments-As-Code.
This makes it easy for anyone to get a ready-to-code workspace for any branch,
issue or pull request almost instantly with a single click.
Similar to prometheus/prometheus#7749.
Signed-off-by: Matthias Rampke <mr@soundcloud.com>
