ESLint - enable pipeline and fix errors

Finally, after a while, I was able to fix all the issues: https://git.drupalcode.org/project/gifplayer/-/merge_requests/8

I'll leave to "needs review" for a while, then I'll move it to "Fixed"

I don't hear any complains from anyone, and no issues mentioned so far, so I'll move this to "Fixed" if anyone doesn't mind.

Automatically closed - issue fixed for 2 weeks with no activity.