Implement text colors in READMEs

[kenorb]

Please implement some possibility of text coloring syntax using Markdown.

Current workarounds: How to add color to Github's README.md file

Related: #369

[kivikakk]

👋 Hi there! Since this issue doesn't relate to the markup gem itself, I'll close it. This came up in #369 and we haven't made any change in decision since then. If you have any other questions or feature suggestions, please reach out to the support team with further questions.