chore(rustfmt): use nightly (#2325)

Stable rustfmt lacks a lot of features resulting in worse formatted
code, thus use nightly formatter.

src/platform_impl/web/web_sys/fullscreen.rs

@@ -58,7 +58,7 @@ pub fn is_fullscreen(document: &Document, canvas: &HtmlCanvasElement) -> bool {
         Some(element) => {
             let canvas: &Element = canvas;
             canvas == &element
-        }
+        },
         None => false,
     }
 }