Allow exprs in the source_file grammar rule

[williamthome]

Closes #3.

Currently, only "top level" forms of a module are allowed at the beginning of the source_file rule, but this makes this tree-sitter not usable, for example, in Markdown code blocks.

Allowing any fragment of an expression makes this tree-sitter usable for other languages to inject Erlang code, for example, a new language in the Phoenix (Elixir) style, that embeeds Erlang code in HTML.

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Notes:

1. The tree generated for fragmented code is (source_file (...exprs)). Maybe the tree as is today as (source_file (...forms)) should be for a file/module structure and (fragment (...exprs)) should be for fragmented parts of code
2. The term "fragment" is what comes to my mind, but could be any other
3. I'm not sure about the conflicts order introduced by this PR

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[alanz]

Thanks for this. It causes a few problems in ELP if we try to use it, for parsing escripts

And the fundamental problem is the shebang causes it to go into error mode, and the prior version recovered gracefully.

I think the solution may be to add an additional form time that parses the shebang.

I am happy to give that a go.

[alanz]

FYI, to check it, in the ELP repo change the tree-sitter-erlang dep to point at this directory (checked out), then run cargo xtask codegen once the tree-sitter-erlang tests pass.

then cargo test --workspace.

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@alanz merged this pull request in bafd09b.