Select_register command should provide visual feedback

[eugenesvk]

select_register command should provide visual feedback (e.g., via a status bar message) after a register is selected
For example, executing select_register then pressing 5 should print "register 5 is selected" or something

[archseer]

We do print count & pending keys in the bottom right (i.e. 33 before pressing g will show up) but looks like we don't do that yet for the register (printing "@ for example)

helix/helix-term/src/ui/editor.rs

Lines 1121 to 1128 in 333c294

	for key in self.keymaps.pending() {
	let s = key.to_string();
	if s.graphemes(true).count() > 1 {
	disp.push_str(&format!("<{}>", s));
	} else {
	disp.push_str(&s);
	}
	}

There's also #980 that will make register selection a bit nicer.

[archseer]

(Prior art, kakoune renders this as reg=@ on the statusline, whereas pending keys render as param=33)