Please add sig(term) signal handler

[igalic]

As a continuation of #9, i would like to see a SIGTERM handler so that a regular shutdown/reboot of my laptop will actually save my work

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n.b.: I've tried to add this myself, but… as I'm only very newly acquainted with Rust, i felt very much out of my waters, especially, since this app doesn't already have any signal handlers, and rust itself has no… standard signal handlers see rust-lang/rfcs#1368 vs https://crates.io/search?q=signal

[igalic]

looking at,

void/src/config.rs

Lines 124 to 135 in 7cdbab0

	#[derive(Debug, Clone)]
	pub struct Config {
	config: HashMap<Key, Action>,
	}
	impl Default for Config {
	fn default() -> Config {
	use termion::event::Key::*;
	Config {
	config: vec![
	(Esc, Action::UnselectRet),
	(PageUp, Action::ScrollUp),

i am imagining an equivalent of HashMap<Signal, Action>

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This is as far as i've gotten: https://gist.github.com/igalic/7773dbc93c45daf0bfb259b48ba1486c#file-signal-diff

the next step would be to modify screen.run() to not just handle_events() but also handle_signals()