Properly implement event loop extension traits

This was implemented for `&dyn ActiveEventLoop` before, but that's less
general than implementing it directly for `dyn ActiveEventLoop`.

The `+ '_` is required to tell the compiler that we want to implement
this for all `dyn ActiveEventLoop`s, not just `'static` ones (even
though they're all going to be `'static`).

src/platform/web.rs

@@ -347,7 +347,7 @@ pub trait ActiveEventLoopExtWeb {
     fn has_detailed_monitor_permission(&self) -> bool;
 }
 
-impl ActiveEventLoopExtWeb for &dyn ActiveEventLoop {
+impl ActiveEventLoopExtWeb for dyn ActiveEventLoop + '_ {
     #[inline]
     fn create_custom_cursor_async(&self, source: CustomCursorSource) -> CustomCursorFuture {
         let event_loop = self