Implement support for some basic attributes for the windows terminal.

[Jezza]

Closes #60.

[Jezza]

You'll probably notice that it doesn't have the full list of values that windows supports as methods, and that's because of how crossterm constructs styles and what the other windows' values are used for.

The values I've omitted, but added explicit members in the enum for are "reset" values, and due to how the styles are constructed, it you can't really construct a line that contains multiple "on"s and "off"s.
Eg, you can't say style("Introducing ").bold().text("Me").reset().text(" and I.") which would output something like "Introducing Me and I."
The ObjectStyles in crossterm don't seem to be built that way, so it makes no sense to add explicit support for the values as methods.
The values themselves are there in the enum, so you could conceivably, chain together multiple object styles, printing them out one by one, and then in that case, the reset would come in handy, but at that point, it might be easier just to wrap that with your own thing....

[Jezza]

Looking back, I think a better solution to this might be doing what Std does.
Have system specific modules, and then just export those based on the system.
That way the user can still access attributes for other systems, as it is possible that someone can use this library for sending terminal seqs over the wire.

[TimonPost]

Nice work!

You mean just allowing the user to execute their own ANSI escape codes?

[Jezza]

Yeah, but do it in a controlled fashion.

format!("{}Inverted{}Normal", Attribute::Inverted, Attribute::Reset)

It doesn't stop people from being stupid, but it didn't do that before.
It just makes composing things easier.

[TimonPost]

Jup that totally true, however, for now, I am fine whit those changes. This should become another PR.