do not add ANSI coloring if stdout is not a tty -- add `--color=auto,yes,no`

[yarikoptic]

It has bugged me for a while, even with original bids-validator and now with deno version: if output is redirected to a file we still get ANSI characters in there which makes viewing requiring special options to less (-R) or otherwise looks horrid:

relates to

• #829

I think by default (with auto), if output is not a tty - there should be no color. Deducing if stdout is tty should be easy, in python like this

❯ python -c 'import sys; print(sys.stdout.isatty(), file=sys.stderr)'
True
❯ python -c 'import sys; print(sys.stdout.isatty(), file=sys.stderr)' > /dev/null
False