You'll need to remove any references to jshint/jscs, update the dependencies in package.json for eslint, configure it to run in Gruntfile.js, and then fix any failures.
The following extensions are candidates for conversion for the purposes of GCI, please check them off if you start working on them:
[ ] Buggy @Zoranzoki21
[ ] CirrusSearch
[ ] CleanChanges
[ ] CodeReview
[ ] CollaborationKit @Pjht
[ ] Disambiguator
[x] DismissableSiteNotice @Zoranzoki21
[ ] GoogleLogin
[ ] GWToolset
[ ] HoverGallery
I can add plenty more extensions if there's demand.
Mentors: @legoktm, maybe @Jdforrester-WMF and @Esanders if they're interested.