Rename completions and remove color information

[bradlc]

• Rename context.completions to context.getClassList – I think this better (1) indicates that it's a function, and (2) describes what the function returns
• Remove colour information from the returned list. While the colour information is useful to an extent, it is complicated to use this information to resolve the colour for classes like hover:bg-red-500 or focus:bg-red-500/30. I have found it simpler to resolve the CSS for a class (using generateRules) and extract the colour from there.

[RobinMalfait]

Removing unused code is always fun! Looking good!