Create unit tests for tree-sitter

[FourierTransformer]

Added some unit tests for tree-sitter. Helps with #27 (still need tests around the symbol extractor to close it out fully)

Unfortunately they don't run in GHA due to the tree-sitter library and headers not being installed. As part of #26, I'm planning on switching over the tree sitter library to one that includes the library, so this external dependency is removed, and these tests will ensure that functionality that is needed remains the same.

[FourierTransformer]

The, "it works on my machine" output:

luarocks test

teal-language-server 0.0.5-1 depends on luafilesystem (1.8.0-1 installed: success)
teal-language-server 0.0.5-1 depends on tl (0.24.1-1 installed: success)
teal-language-server 0.0.5-1 depends on lua-cjson (2.1.0.10-1 installed: success)
teal-language-server 0.0.5-1 depends on argparse (0.7.1-1 installed: success)
teal-language-server 0.0.5-1 depends on inspect (3.1.3-0 installed: success)
teal-language-server 0.0.5-1 depends on luv (1.48.0-2 installed: success)
teal-language-server 0.0.5-1 depends on lusc_luv >= 4.0 (4.0.1-1 installed: success)
teal-language-server 0.0.5-1 depends on ltreesitter (0.0.7-1 installed: success)
teal-language-server 0.0.5-1 depends on tree-sitter-cli (0.24.4-1 installed: success)
teal-language-server 0.0.5-1 depends on tree-sitter-teal (0.0.32-1 installed: success)

teal-language-server 0.0.5-1 depends on busted ~> 2 (2.2.0-1 installed: success)
●●●●●●●●●●●●●●●●●●
18 successes / 0 failures / 0 errors / 0 pending : 0.038159 seconds