Allow customization of badges

[rohan-at-sentry]

@drazisil-codecov works like a charm, thanks for helping me! See README

I would just like to ask you if you could check with your colleagues (if you are not yourself in charge ofc ) if you can add support for customizing the "badge text", which was requested on community.codecov 2 years ago. Since it is not possible today, I had to make this somewhat ugly markdown table for my badges:

This would be very pretty if I could use the flag value as the text of the badge (or fully customized).

Originally posted by @Sajjon in #308 (comment)
Related #106, which however doesn't appear to cover changing the text on the badge