feat: include placeholder

see #493

Author: faretek1

scratchattach/__init__.py

@@ -32,5 +32,6 @@
 from .site.user import User, get_user, Rank
 from .site._base import BaseSiteComponent
 from .site.browser_cookies import Browser, ANY, FIREFOX, CHROME, CHROMIUM, VIVALDI, EDGE, EDGE_DEV, SAFARI
+from .site.placeholder import PlaceholderProject, get_placeholder_project
 
 from . import editor