BM25 from treesitter function calls

[mpadge]

Use code from ropensci-review-tools/pkgstats#62 (comment) to get all function call tags from tree-sitter, and then use all of those in a separate BM25 analysis

---

TODO

• Add tests
• Upload binary data
• Use those data to calculate separate BM25 measure
• Incorporate this code-based BM25 with embedding similarities to generate final similarity metric for code

[mpadge]

Re-opening to add tests

[mpadge]

Re-opening to remove all Recommended pkgs from DESC file, and to use asNamespace() to get function names, and not requireNamespace(). The former just reads the namespace file from .libPaths without loading at all.