Allow forcing colors

[GerkinDev]

Hi,

I run angular CLI tasks in my own scripts that internally use concurrently. This setup disables colors in the angular CLI issue.

It would be great to be able to force color support via an env var, like FORCE_COLOR.

Related to:

• Flag to disable build/serve colors for text viewers that don't support them #6478
• Unexpected color changes in Angular commands' output open-cli-tools/concurrently#238

[alan-agius4]

FORCE_COLOR is supported by Node.js natively without the need to implement addition logic. See: https://nodejs.org/dist/latest-v12.x/docs/api/tty.html#tty_writestream_getcolordepth_env

The problem here, is that concurrently,stdout implementation doesn't implement Node.js WriteStream, instead it is using RxJs Subject https://github.com/open-cli-tools/concurrently/blob/10ff00cbfbd4dbf1a41a716556b4592a20022fa9/src/command.js#L21 which of course doesn't support the getColorDepth nor FORCE_COLOR APIs.