Allow Colors to be created from 3-digit hexadecimal codes

[FrankRay78]

A Color can be created from a 6-digit hexadecimal code, either by FromHex or TryFromHex methods.

Support should be added for 3-digit hexadecimal codes.

eg. #09C which is the short version of #0099CC

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Please upvote 👍 this issue if you are interested in it.

[TheMarteh]

This seems like a relatively easy fix that I'll try to pick up as my first issue.

It seems that we are able to expand the original fromHex method, by taking the sanitized string, checking it for 3 characters, and doubling those.

[FrankRay78]

Great @TheMarteh, I'll be the reviewer/your buddy. Don't hesitate to ask along the way.

[TheMarteh]

Thanks a lot, @FrankRay78 . I've opened up PR #1708 with the implemented changes.