Using Tree-sitter predicates requires us to use Topiary capture names

[Xophmeister]

Tree-sitter comes with a bunch of built-in predicates, which work using the capture names. However, in Topiary, we only allow our formatting capture names, such as @append_hardline, etc. While these work in the predicates, it makes them a bit strange to read. For example:

; Append a space to (foo (bar)) nodes if they begin with a capital letter
(foo
  (bar) @append_space

  (#match? @append_space "[A-Z].*")
)

While this would just be a nice-to-have, maybe it would be worthwhile whitelisting certain patterns for capture names that have no formatting functionality, but make the predicates more intuitive. For example, allowing @topiary\..+:

(foo
  (bar) @topiary.foobar @append_space

  (#match? @topiary.foobar "[A-Z].*")
)

A potential issue with this is that, IIRC, the number of capture names per node is limited to something unreasonably small (like 3).