Add ditto-highlight crate 💅

[jmackie]

I reckon this will come in useful.

If nothing else, it was useful for testing the highlight queries in tree-sitter-ditto.

[codecov]

Codecov Report

Merging #107 (bac5023) into main (761834f) will increase coverage by 0.39%.
The diff coverage is 70.00%.

@@            Coverage Diff             @@
##             main     #107      +/-   ##
==========================================
+ Coverage   84.66%   85.06%   +0.39%     
==========================================
  Files          82       83       +1     
  Lines       14858    14880      +22     
==========================================
+ Hits        12579    12657      +78     
+ Misses       2279     2223      -56     

Impacted Files	Coverage Δ
crates/ditto-lsp/src/semantic_tokens.rs	0.00% <0.00%> (ø)
crates/ditto-tree-sitter/src/lib.rs	71.42% <ø> (ø)
crates/ditto-highlight/src/lib.rs	93.90% <93.90%> (ø)
crates/ditto-lsp/src/bin/ditto-lsp-testbin.rs	1.75% <0.00%> (+1.75%)	⬆️

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