Add SetCursorStyle command

[TimonPost]

Adds a command to set the cursor style.

Fixes: #646 , maybe #740

[Cl00e9ment]

I was just about to create a pull request but you were faster!

I don't know if it's useful, but here is my version:
branch: https://github.com/Cl00e9ment/crossterm/tree/feat-set-cursor-style
diff: https://github.com/crossterm-rs/crossterm/compare/master...Cl00e9ment:crossterm:feat-set-cursor-style?expand=1

[TimonPost]

Oh whoops, just merged and your commented showed up. What a coincidence, im sorry :), let me look at that.

[TimonPost]

I decided to keep enable / disable blinking. Those are very specific and a user might not know which cursor shape it uses. Allowing to have this separately may allow a user to control blinking for the current active cursor

[TimonPost]

If you want to follow up and improve there is time to do that! I will not release yet. I see I missed adding it to the commands list and your comment on why two ansi codes are used might be nice as well.

[Cl00e9ment]

I decided to keep enable / disable blinking. Those are very specific and a user might not know which cursor shape it uses.

Yes but these commands are broken on certain terminals so a note should be added.

If you want to follow up and improve there is time to do that!

I'll do that!