Allow default export for any declaration (extension of #160)

[mjambon]

Implements suggestion from pending PR #160 (review)

[mjambon]

EDIT: nevermind, I fixed it

Hmm, CI is giving us an error that I don't get on my machine:

export default function () { }
export default function name1() { }

is expected to be parsed into

  (export_statement
    (function (formal_parameters) (statement_block)))
  (export_statement
    (function_declaration (identifier) (formal_parameters) (statement_block)))

but CI finds a function instead of a function_declaration:

  (export_statement
    (function (formal_parameters) (statement_block)))
  (export_statement
    (function (identifier) (formal_parameters) (statement_block)))

1. I don't know what I did wrong or what CI is doing different than me. I'm using tree-sitter 0.19.4. This is strange.
2. Both interpretations seem valid since after default we allow a declaration (including function_declaration) or an expression (including function). I don't see a dynamic conflict being declared, and even if this was a case of dynamic conflict resolution, can it be non-deterministic?

[mjambon]

I had forgotten to regenerate the parser after having undone/redone a bunch of times... This time it should work.

[mjambon]

I just removed a conflict declaration that was left over by accident. The diffs are simple now.

[mjambon]

ok, I'm merging this because there's nothing left that's controversial, and I'll close the original PR by @resolritter .