cargo pgx schema uses XTERM colors

[Hoverbear]

Recently @eeeebbbbrrrr noticed on Mac's default Terminal.app (which doesn't include true colour support), cargo pgx schema would produce this undesirable output:

This is because it only supports 256 colors. 😢

So, instead, we mimic what the wonderful (also MIT licensed) bat does: sharkdp/bat@3099f51#diff-23172669e56dbc175323aa1386ecc2d11a9dcd38b561e822867eba12cc7b6434

Now cargo pgx schema uses a theme and the also-excellent owo-colorize's XTermColor functionality to use the users preferred terminal colors.

terminal.app:

On terminals where one can change the colour scheme without opening a new tab, it also adapts to these changes.

My Palenight theme on VsCode:

Changing the scheme (nothing else):