Nested double quotes break highlighting in .eex files

[optikfluffel]

Example from a newly generated Phoenix project with broken highlighting on lines 8, 20 and 29:

[josevalim]

Yeah, this has been annoying the hell out of me. :/ but I haven't had the time to take a proper look at it yet. If you could take a look at it, it would be great! ❤️