Add support for the BibTeX file format

[schneiderfelipe]

This PR does three things:

• Adds an entry to language.toml (using https://github.com/latex-lsp/tree-sitter-bibtex/commit/ccfd77db0ed799b6c22c214fe9d2937f47bc8b34)
• Adds queries from the same repo
• Adds a formatting configuration that uses FlamingTempura/bibtex-tidy

Out of the three, the most opinionated is probably the last one. Let me know if there's anything to add or remove.