Make sail-mode.el comment variables buffer-local

[darius1702]

This is just a small thing but has been bugging me a bit:

Without the setq-local, variables like comment-end persist between buffers and calling for example comment-line in elisp-mode produces ;; text **/ after sail-mode was activated in another buffer.

[github-actions]

Test Results

   12 files  ±0     26 suites  ±0   0s ⏱️ ±0s
  768 tests ±0    768 ✅ ±0  0 💤 ±0  0 ❌ ±0 
2 714 runs  ±0  2 714 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit b3c8817. ± Comparison against base commit 0d53955.

[bacam]

Thanks!