feat: add check-compat-table script and feature limits tests

[zerdos]

This pull request introduces safeguards to ensure the compatibility tables and feature flags remain within their supported limits, and adds a Makefile check to help maintain up-to-date compatibility tables. These changes help prevent subtle errors due to bitmask overflows and improve developer workflows.

Feature flag capacity safeguards:

• Added a warning comment and a compile-time assertion in js_table.go to ensure the JSFeature bitmask does not exceed 64 features, preventing silent overflow errors.
• Added a test in compat_test.go to check that jsTable and cssTable do not exceed their respective bitmask capacities (64 for JS, 16 for CSS), providing clear error messages if limits are breached.

Developer workflow improvements:

• Added a check-compat-table Makefile target to verify that js_table.go and css_table.go are up to date, alerting developers when changes need to be committed.