Add limit to minimum window size (#13126)

Release Notes:

- Add a limit to the minimum window size on macOS.

Here's the minimum window before change:
<img width="121" alt="image"
src="https://github.com/zed-industries/zed/assets/38318044/9e907194-42e5-457e-91ea-96613426b479">

After change:
<img width="410" alt="image"
src="https://github.com/zed-industries/zed/assets/38318044/6e9c3057-9860-4f4b-9a73-c158ebac5ba9">

crates/gpui/src/geometry.rs

@@ -2287,6 +2287,15 @@ impl Pixels {
     pub fn abs(&self) -> Self {
         Self(self.0.abs())
     }
+
+    /// Returns the f64 value of `Pixels`.
+    ///
+    /// # Returns
+    ///
+    /// A f64 value of the `Pixels`.
+    pub fn to_f64(self) -> f64 {
+        self.0 as f64
+    }
 }
 
 impl Mul<Pixels> for Pixels {