Fix node naming in {param,field}_declaration

[adonovan]

This change commutes the field(...) and commaSep(...) operations so that the commas don't get named.
The set of accepted inputs has not changed.

Fixes #45

Checklist:

• All tests pass in CI.
• There are sufficient tests for the new fix/feature.
• Grammar rules have not been renamed unless absolutely necessary.
• The conflicts section hasn't grown too much.
• The parser size hasn't grown too much (check the value of STATE_COUNT in src/parser.c).

[maxbrunsfeld]

Thanks for fixing this. I left one stylistic suggestion.

[maxbrunsfeld]

Can you update the generated parser by running tree-sitter generate? We currently check the generated code into these repositories.

[adonovan]

Can you update the generated parser by running tree-sitter generate? We currently check the generated code into these repositories.

Done. Is there a document that explains the usual contributing process to which I can link the README?

[aryx]

This need to be rebased from the latest.
Sorry for accepting this a bit later than your other PRs.