[Support] Update a language grammar.

[7ombie]

In response to #2033, I mentioned a few issues with Swift support, and @Dispersia gave me some pointers on how to update the grammar and make a PR. I've made a start, but ran into a Helix-specific issue, and didn't want to keep asking @Dispersia for advice.

I cloned the Swift TreeSitter project and Helix, set HELIX_DEFAULT_RUNTIME to the runtime directory inside the Helix repo, then built Helix from source. That seemed to work fine.

I then edited .../runtime/queries/swift/highlights.scm within the Helix repo, making a few changes, based on the tree-sitter-swift version of highlights.scm. I also updated languages.toml to point to the newest commit hash for their project:

[[grammar]]
name = "swift"
source = { git = "https://github.com/alex-pinkus/tree-sitter-swift", rev = "1c586339fb00014b23d6933f2cc32b588a226f3b" }

When I tried to rebuild Helix (using cargo install --path helix-term --locked) it failed with this message:

  Failure 1/1: swift Failed to compare source and binary timestamps

  --- stderr
  thread 'main' panicked at 'Failed to compile tree-sitter grammars: 1 grammars failed to build', helix-term/build.rs:7:14

I don't know how to address this, and can't find any more information. I don't know Rust either, so am not familiar with Cargo etc. Any advice would be appreciated. Thanks.