Sketch in a table for the keybindings UI (#32436)

Adds the initial semblance of a keymap UI. It is currently gated behind the `settings-ui` feature flag. Follow up PRs will add polish and missing features.

Release Notes:

- N/A

---------

Co-authored-by: Ben Kunkle <ben@zed.dev>
Co-authored-by: Anthony <anthony@zed.dev>

crates/zed/src/zed.rs

@@ -1429,6 +1429,8 @@ fn reload_keymaps(cx: &mut App, mut user_key_bindings: Vec<KeyBinding>) {
         "New Window",
         workspace::NewWindow,
     )]);
+    // todo: nicer api here?
+    settings_ui::keybindings::KeymapEventChannel::trigger_keymap_changed(cx);
 }
 
 pub fn load_default_keymap(cx: &mut App) {