Fix Cursor Unlock on Web

A tiny plugin that fixes Bevy not reporting when the cursor is unlocked on web

Usage

Just add the plugin, that's it:

use bevy::prelude::*;
use bevy_fix_cursor_unlock_web::prelude::*;

App::new()
  .add_plugins(DefaultPlugins)
  .add_plugins(FixPointerUnlockPlugin);

Now, Window::cursor_options::grab_mode is automatically set to CursorGrabMode::None for you when unlocking the cursor on web.
This fixes https://github.com/bevyengine/bevy/issues/8949