Editor: Add shortcut to toggle line numbers (#8642)

Following #7665, I've added a keymap to quickly hide and show gutter
line numbers.

`ctrl-l` and `cmd-l` were taken, so I've bound it to `cmd-;`. 



https://github.com/zed-industries/zed/assets/138762/365d2a7c-b775-4486-8389-edafe59b2a87

Release notes:

- Added `editor: toggle line numbers` command and default keybindings
(`cmd-;` on macOS).

---------

Co-authored-by: Thorsten Ball <mrnugget@gmail.com>

crates/editor/src/editor_settings.rs

@@ -2,7 +2,7 @@ use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
 use settings::Settings;
 
-#[derive(Deserialize)]
+#[derive(Deserialize, Clone)]
 pub struct EditorSettings {
     pub cursor_blink: bool,
     pub hover_popover_enabled: bool,