Support bright colors in config

**Is your feature request related to a problem? Please describe.**
Unless I'm mistaken and it's not documented well, there's no way to use bright colors in the config of lazygit/lazydocker.

**Describe the solution you'd like**
Add `bright` modifier that makes the chosen color use the bright version instead and send proper ANSI codes for that.

**Describe alternatives you've considered**
You can in theory set any color with hex value, but that's not the same - I'd like to use the same bright color as defined in terminal.