Allow path for grammar source

[ErinvanderVeen]

Allow specifying grammars through prebuild parsers

Description

Previously, Topiary was forced to fetch the grammar repositories and build the grammars manually. This PR adds the option to specify a path to a grammar binary file.

Additionally, it adds the topiary-cli-nix build output, that doesn't fetch any grammars manually.

Checklist

Checklist before merging:

• CHANGELOG.md updated
• README.md up-to-date

[Xophmeister]

I've made a few comments about the README, but otherwise it looks good 👍

Although, I don't really follow the Nix-stuff, so you may want a second opinion.

[yannham]

FYI, I'm trying that as part of a flake.lock update on the Nickel side. Will report if there is any issue with the new -nix only entry.

[yannham]

One major issues is that the grammar from nixpkgs aren't necessarily up-to-date, so the queries don't match. This might not be the case for more stable grammars, but for example this is the case for the Nickel grammar, to topiary-cli-nix binary isn't able to format Nickel currently. A dirty fix is to take the tree-sitter-nickel grammar as a separate argument that we can pull from the nickel-lang/tree-sitter-nickel flake directly, in the meantime, because I tried to update the grammar upstream directly in Nixpkgs but the process is really not obvious.

[yannham]

I've pushed my work-around to use the right Nickel grammar. I don't know if this needs to be done for other grammars as well,I haven't tried them all.

[Xophmeister]

@yannham Your changes look good to me insofar as I can judge, but I trust you so feel free to consider this approved if it's critical for Nickel.

[yannham]

In the end I could get rid of the Nixified version of Topiary from the Nickel build altogether, so this isn't as critical as before, if you prefer to wait for another look from @ErinvanderVeen or someone else.

[nbacquey]

I'm not proficient enough in Nix to certify this part of the changes.
But in the meantime, the ability to specify a compiled grammar is useful in itself. I would advocate to merge now, and possibly revise the Nix stuff later, should the need arise.

[ErinvanderVeen]

I'd like to keep the Nixified version as well for now. It doesn't reduce the functionality or behaviour of any other part of Topiary.