[draft] Add Bracketed Paste Events

[sigmaSd]

#545

Couple of points:

• I can flatten PasteEvents(Vec<Event>) to become PasteEvent(String)
• I'm not sure how to restore Copy bound to Event
• I think for winapi I should just stub it with Ok(())
• Is flushing events like this https://github.com/crossterm-rs/crossterm/compare/master...sigmaSd:add_brakceted_paste_mode?expand=1#diff-835dd5a0632e3b0d7b10539464274511152432fac2dce69a999604c76c86f0f9R128 Ok?

[sigmaSd]

To not flush the events I need to detect BracketdPasteStart/End here https://github.com/crossterm-rs/crossterm/blob/master/src/event/source/unix.rs#L76 but I think they're being filtered? I would appreciate some pointers there.

The idea if i detect them at that point I can

• Add to UnixInternalEventSource struct, a pate_flag and paste_buffer
• If the event at line 76 is BracketedPasteStart set paste_flag to true
• if paste_flag is true, push the received event at line 76 to paste_buffer and don't early return
• If the event at line 76 is BracketedPasteEnd set paste_flag to false, return Event(PasteEvent(self.paste_buffer.drain())

[sigmaSd]

closed in favor of #693