Support for format_args_capture feature

[rod-stuchi]

The format_args_capture was stabilized in 1.58.0.

It would be nice to resolve the captured identifiers.

[nik-rev]

I made a separate tree-sitter grammar for Rust's string interpolation macros that use format_args!.

Grammar: https://github.com/nik-rev/tree-sitter-rust-format-args/tree/main
It is used in Helix: helix-editor/helix@1023e8f

Example with syntax highlighting: