feat: add line numbers back to coverage.json

[bcoe]

Lands #5

Thanks for the contribution @nowycheung, landed here because I created a pretty brutal merge conflict polishing off the monorepo structure.

[coveralls]

Coverage decreased (-0.2%) to 91.569% when pulling 055e328 on line-numbers into 212cbea on master.

[bcoe]

@nowycheung I've released your work in:

npm cache clear; npm i babel-plugin-istanbul@next

Could you try installing and let me know if this does the trick for you?

[nowycondro]

It works now, thanks you so much @bcoe.