Fontbakery: Check if OFL.txt contains copyright string

[m4rc1e]

An OFL.txt file's first line should be the font copyright e.g "Copyright 2019 The Montserrat Project Authors (https //github.com/julietaula/montserrat)"

We just pushed https://github.com/google/fonts/pull/2323 and it didn't contain this line. I don't think we have an FB check to catch this.

cc @bghryct

[m4rc1e]

This issue could be bundled with #2688

[felipesanches]

thanks, @m4rc1e!

[m4rc1e]

Thanks to @bghryct for finding these edge cases.

[bghryct]

@m4rc1e that's a polite way of saying i did an oops

[m4rc1e]

Nah, the checks should catch it.

[felipesanches]

And they will do it! Very soon ;-)

[felipesanches]

The google/fonts repo has a poor record on these criteria... lets hope we can improve it by having this check in place ;-)