Don't send permessage-deflate header if not supported

[code-asher]

I have no idea if this fixes #2975 since I don't have a way to test.

TODOS

• create follow-up issue to enable e2d testing on Safari to catch this in the future (@jsjoeio) [dev]: enable end-to-end test suite on Safari and Firefox #2998

[code-asher]

The sed examples in that issue set permessageDeflate to false and comment out the response header.

However, I'm not sure why permessageDeflate is set to false. Is Safari reporting that it supports permessage-deflate when it doesn't really?

[jsjoeio]

Seeing if I can help out by testing locally on my iPad:

1. gh pr checkout 2993
2. yarn && yarn watch --link - run with code-server link to be able to access from iPad
3. open in Safari on iPad

[jsjoeio]

Before this change

Reproducing on main i.e. 3.9.2 - blank screen. Won't load.

After this change

Pulled down this branch and ran fine without issues

IMG_0201.MP4