Add Stylize methods directly to Style

[joshka]

Problem

I'd like to be able to write:

const FOO: Style = Style::new().green().bold();

But trait methods can't be const.

Solution

Add the Stylize methods directly to the Style type rather than implementing them via Stylize.

Alternatives

Additional context

[g4titanx]

where can the Style type be found in the codebase?

[joshka]

I'd like to get buy-in / thoughts from the other maintainers before implementing this. I've removed the good first issue label for now.

[g4titanx]

alright