Create "custom syntax" package to enable linting with Stylelint

[srmagura]

Hello, Emotion contributor here. Wanted to make you aware of this feature request: emotion-js/emotion#2695

I know very little about this, but seems like it could be possible to make a single custom syntax that works for both SC and Emotion. Or at least we could make 2 packages that share some of the code. Very low priority issue for me personally but if someone wants to tackle this that would be rad.

[karlhorky]

In the meantime, there have been two custom syntaxes published 🎉🙌

• postcss-styled-syntax by @hudochenkov customSyntax for Stylelint v14+ #3897 (comment)
• postcss-styled-components by @43081j customSyntax for Stylelint v14+ #3897 (comment)

I would suggest that anyone looking to set up Stylelint with Emotion or Styled Components to try these out!

Super big thanks to @43081j and @hudochenkov for putting in the work to get these out the door!