Support EnableColorSelection feature in Terminal

The legacy conhost has a (somewhat hidden, I think) feature called "color selection", which allows you to select text and then use some keystrokes to change the fg/bg color of the selected text (including optional search). (for a description, see here)

This feature is not on by default, and must be enabled by setting a registry value.

I LOVE this feature and use it all the time (and when people see me use it, they all want to know how to turn it on). Hence I would love to port this feature to Terminal as well.

Proposed technical implementation details

I think this would probably need to be disabled by default, and only enabled by a profile setting. Based on a recent comment by Dustin, I believe he has an aversion to things that manipulate the buffer, but I don't know why that might be considered undesirable, or what other options might be--if you want this particular selection to be green, then you have to store that information somewhere--why not in the buffer; if not in the buffer, then where?

If the team is not opposed to having optional support for this feature, I'd be interested in taking a stab at it. I would appreciate any pointers to help me get a toe-hold in the code.