Setup 1.x Tugboat preview

Problem/Motivation

It would be helpful to be able to test the 1.x branch without setting up a local and keeping it up to date on a regular basis.

Proposed resolution

From @q0rban: Currently the built-in d.o integration is only visible for merge requests, however one option that some folks do is mirror their d.o gitlab repo to cloud GitLab or GitHub and then set up their own Tugboat integration there... @mherchel has done this sort of thing before with Olivero theme.