Previously, we only used bright colors when the bold attribute was set.
We now have the option to set it via escape sequences. We also needed to
make the bold text behavior optional, as some color schemes do weird
things with it. For example, Solarized uses it for various shades of
gray, so bold green would turn into a light shade of gray.
The following new escape sequences are supported:
- `CSI 90;m` to `CSI 97;m`: set bright foreground color
- `CSI 100;m` to `CSI 107;m`: set bright background color
Previously, we converted colors to their RGB values immediately when
they were set. This meant that their semantic meaning was lost, we could
not tell a precise RGB value apart from a named/indexed color.
The new way of storing colors will allow us to retain this information,
so we can change a color scheme on the fly, and previously emitted text
will also be affected.
