Support class static blocks

[Shraymonks]

Add support for static blocks in classes. Fixes #222

References:
MDN
TC39 spec

Checklist:

• All tests pass in CI.
• The script/parse-examples passes without issues.
• 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).

[aryx]

you can probably rebase on latest to fix the windows CI failure.

[Shraymonks]

you can probably rebase on latest to fix the windows CI failure.

Rebased!

[maxbrunsfeld]

Thanks! Just one suggestion.