Increase font size in CSDs on Wayland

Winit changed the default font size for CSDs from 17pt to 11pt, this
patch reverts that since it is too small to be readable.

alacritty/src/wayland_theme.rs

@@ -67,6 +67,10 @@ impl WaylandTheme for AlacrittyWaylandTheme {
             (_, Button::Close) => self.hovered_close_icon,
         }
     }
+
+    fn font(&self) -> Option<(String, f32)> {
+        Some((String::from("sans-serif"), 17.))
+    }
 }
 
 trait IntoARGBColor {