Separate turing.ml site from Turing.jl

[cpfiffer]

This PR makes it so that the build process for turing.ml is distinct from Turing.jl. Currently, all the website files live inside Turing's docs folder, which has various disadvantages.

Most of the work in the PR shows up in make.jl and a little bit in make-utils.jl. Everything else is largely copied over from Turing.jl/docs. To summarize the new build process:

1. Each time a commit shows up on this repo or on the 23rd hour of every day, a GitHub Action is triggered.
2. The GH action builds the current master of Turing, and then rebuilds whatever the most recent released version is.
3. During the build process, make.jl will build the site in a temporary folder and copy all the relevant documents to it. Documenter.jl deploys the docs from this temporary folder.

The idea is to keep everything that needs to be "stateful" in Turing.jl, such as the guides and documentation, and everything that always needs to be current (like the blog or list of team members) in this repo. We also don't really want to have much/any HTML in Turing.jl, which this PR also handles. I will remove all the stuff we don't need in Turing once this repo is functional.

Note that this won't actually change the site when the PR goes through, since GitHub is still configured to serve the site from Turing.jl. I assume there will also be some headaches as we transition over, but I won't know until we merge this in.

[trappmartin]

Maybe @debug instead?

[cpfiffer]

Well, I'd rather be able to see it in the build logs without setting any other environment variables. It's pretty rare that this would be run by a human.

[yebai]

The idea is to keep everything that needs to be "stateful" in Turing.jl, such as the guides and documentation, and everything that always needs to be current (like the blog or list of team members) in this repo.

Seconded - this looks like a sensible separation between docs (Turing.jl and related libraries) and website (appearance, blog, news etc.).

Note that this won't actually change the site when the PR goes through, since GitHub is still configured to serve the site from Turing.jl. I assume there will also be some headaches as we transition over, but I won't know until we merge this in.

To clarify a bit: does this mean the resulting output is pushed to the gh-pages branch of Turing.jl?

[yebai]

Great work - thanks @cpfiffer! I left two minor questions in the comments section.

[cpfiffer]

To clarify a bit: does this mean the resulting output is pushed to the gh-pages branch of Turing.jl?

Not quite. Both TuringLang/turing.ml and TuringLang/Turing.jl have a gh-pages branch, and each are currently spitting out documentation to their respective branches. Eventually we want to shut down the Turing.jl:gh-pages branch and redirect GitHub Pages to this repository instead.