Add Caps Lock support (#30470)

Closes #21700

Release Notes:

- Added caps lock support and show a warning if the user is entering an
SSH password with Caps Lock enabled

---------

Co-authored-by: Mikayla Maki <mikayla@zed.dev>
Co-authored-by: Mikayla Maki <mikayla.c.maki@gmail.com>
Co-authored-by: 张小白 <364772080@qq.com>

crates/gpui/src/platform.rs

@@ -415,6 +415,7 @@ pub(crate) trait PlatformWindow: HasWindowHandle + HasDisplayHandle {
     fn display(&self) -> Option<Rc<dyn PlatformDisplay>>;
     fn mouse_position(&self) -> Point<Pixels>;
     fn modifiers(&self) -> Modifiers;
+    fn capslock(&self) -> Capslock;
     fn set_input_handler(&mut self, input_handler: PlatformInputHandler);
     fn take_input_handler(&mut self) -> Option<PlatformInputHandler>;
     fn prompt(