console: add support for %c style formatter in console.log()

[humphd]

Node's console currently supports a number of formatters, s, j, d, o, O, i, f. However, it doesn't support %c:

> console.log('%cHello World', 'color:green; background:yellow;')
%cHello World color:green; background:yellow;

The same code in Safari, Firefox, and Chrome does this:

The Console spec doesn't give a ton of help on what %c should do, other than to say that it "Applies provided CSS."

Obviously there are aspects of this that don't make sense in the terminal vs. a browser, but perhaps some of it does? It would be nice if node's console could do more than ignore %c.

Apologies if this has come up in the past and been rejected. I wasn't able to find a previous discussion.

[devsnek]

Technically possible but we'd need to bring in a CSS parser, map all the ANSI stuff, etc...

What if we just strip out %c formatting entirely:

> console.log('%cHello World', 'color:green; background:yellow;')
Hello World

[jasnell]

For now, I'd say stripping out the %c formatting is the better approach.