Various fixes for JSX support

[guillaumebrunerie]

This pull request brings the changes from tree-sitter/tree-sitter-javascript#227 to the Typescript grammar, and fixes what needs to be fixed in the grammar and tests here.

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).

[guillaumebrunerie]

Looks like I had forgotten one change related to fragments, I've added it now and a test to make sure that fragments behave properly.