Structure Query

[mattmassicotte]

This introduces a "structure.scm" query definition.

I use this for two things: highlighting of related syntactic elements and indentation. The first implementation was for the highlighting only. But, as I began working on tree-sitter-backed indentation, I realized that they were almost the same underlying problem.

The query defines the following labels:

• structure.anchor: the beginning of a structural element
• structure.open: the opening of a scope
• structure.close: the closing of a scope
• structure.separator: a separator within a scope
• structure.limit: the closing of scope that isn't itself part of the parent structure

I'm not sure how you might feel about something like this. But, I figured I'm using it with great success, so I might as well let you have a look. Absolutely no worries if you don't think this belongs in the parser repo. And, if you have any feedback, that would be great too!

Checklist:

• All tests pass in CI.
• There are sufficient tests for the new fix/feature.
• Grammar rules have not been renamed unless absolutely necessary.
• The conflicts section hasn't grown too much.
• The parser size hasn't grown too much (check the value of STATE_COUNT in src/parser.c).

[mattmassicotte]

Thank you so much!