test: added failing test for postcss-hexrgba plugin

[Techn1x]

Hey! I noticed for my project when postcss-simple-vars is updated from 6.0.2 to 6.0.3, the postcss-hexrgba plugin fails to convert hex color codes to the rgba values needed.

I wrote this failing test so we can see if it's something to do with this plugin, or something awry in hexrgba.

The changes between 6.0.2 and 6.0.3 didn't look that substantial so I am not sure what broke... 🤔

[Techn1x]

The second line is the expected output, but on 6.0.3 it incorrectly outputs .a { color: rgba(#FF0000,0.10); }

[sampullman]

@Techn1x Yes, it's a problem with postcss-hexrgba, the relevant issue is: madeleineostoja/postcss-hexrgba#31

This PR fixes the issue: madeleineostoja/postcss-hexrgba#33

Ideally it would get merged but the maintainer seems inactive. In my personal projects I'm temporarily using the above PR branch as a dependency:

"postcss-hexrgba": "github:hudochenkov/postcss-hexrgba#migrate-to-postcss-8"

[Techn1x]

Thanks for the quick reply! I'll give that branch a go, thanks a bunch.

[ai]

I am closing this PR since postcss-hexrgba must be moved to PostCSS 8. There is no way to fix it here.

[Techn1x]

The postcss-hexrgba was just updated to postcss 8 (v2.1.0) and the issue goes away! Thanks everyone.