Add release tarball with sources including submodules

[jirutka]

The source code tarballs that GitHub automatically generates (e.g. https://github.com/afnanenayet/diffsitter/archive/refs/tags/v0.6.6.tar.gz) don’t include git submodules.

Can you please pack tarball with all sources, including submodules, as part of the release process? This will make it easier for Linux distributions to package diffsitter.

[afnanenayet]

Is this still as necessary now that diffsitter supports dynamically linking against grammars? Some other people have expressed that they'd rather package the tree-sitter libraries separately and have the diffsitter package depend on them. If you still want a tarball with all submodules, happy to work on it.

[jirutka]

Yes, I’ll still appreciate tarball with the submodules.