fix(jsx-email): assert comma color function notation for Tailwind

[shellscape]

This PR contains:

• [x] bugfix
• [ ] feature
• [ ] refactor
• [ ] documentation
• [ ] other

Are tests included?

• [x] yes (bugfixes and features will not be merged without tests)
• [ ] no

Breaking Changes?

• [ ] yes (breaking changes will not be merged unless absolutely necessary)
• [x] no

If yes, please include "BREAKING CHANGES:" in the first commit message body, followed by a description of what is breaking.

List any relevant issue numbers: Fixes #97

Description

This issue fixes #97 by applying a post processor to generated CSS in the Tailwind component, and enforces use of comma separated notation for color functions, as many prominent email clients don't support other notation styles. https://www.caniemail.com/features/css-rgb/