feat(tests)!: new infrastructure based on makefile

Problem: Not easy to run all checks and tests locally. Redundant CI
workflows.

Solution: Separate CI into two workflows:
 * lint: Lua files (stylua, luals), query files (valid captures,
   predicates, directives using tsqueryls), docs
   (SUPPORTED_LANGUAGES.md) -- does not need parser installation
 * tests: parsers (ABI compatibility), query files (tsqueryls on
   Linux/macOS; nvim on Windows), highlight and indent tests (separated
   for better readability) -- needs parser installation (but only once)

Switch to https://github.com/nvim-treesitter/highlight-assertions fork
with ABI 15 support.

Run all tests (on Linux and macOS) through `make` (`formatlua`,
`checklua`, `lintquery`, `formatquery`, `checkquery`, `docs`, `tests`),
which downloads and caches all necessary dependencies.

Remove `update-readme` workflow (replaced by lint job on PRs).