Version 12 Breaking changes list

Much like #2558 but for version 12. This is not a discussion.

- [ ] changelog/release notes should link to the upgrade / breaking changes guide
- [x] #3527
- [x] remove vuePlugin from developer tool
- [x] #3526
- [x] `classNameAliases` => `scopeAliases`
- [x] directory `styles` => `themes`
- [ ] #3528
- [ ] Our default themes (both light and dark) should be WCAG AA accessible re: contrast
- [x] Revisit #3470 and the idea of a index to make importing multiples languages easier
- [ ] #3483
- [x] Change all Windows CRLF To Linux "standard" CR-only line encoding #3298
- [x] stop shipping `scss` folder in Node build, use `themes/*.css` folder instead - it's the same content
- [x] fix default padding of `.hljs` (why is it 2px 3px???)
- [ ] add default font-size for themes
- [x] remove old style `highlight` that was deprecated in 10.7 API Related: #2277