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/keystroke.rs

@@ -538,3 +538,11 @@ impl Modifiers {
             && (other.function || !self.function)
     }
 }
+
+/// The state of the capslock key at some point in time
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Default, Serialize, Deserialize, Hash, JsonSchema)]
+pub struct Capslock {
+    /// The capslock key is on
+    #[serde(default)]
+    pub on: bool,
+}