[RFC] Add Bibtex support to load_data()

Feature requests
1

I’ve implemented a Bibtex loader on top of nom-bibtex, and would like to submit a PR.

I haven’t made any documentation yet, but can do so if you’re interested. The generated data structure is pretty much what nom-bibtex generates, so it’s simple to use.

2

I’ve just added documentation for bibtex format in my fork.