Added Filters.all (#464)

Useful filter to use as default value when extending Handler class

pyrogram/client/filters/filters.py

@@ -65,6 +65,9 @@ class Filters:
 
     create = create
 
+    all = create(lambda _, m: True, "AllFilter")
+    """Filter all messages."""
+    
     me = create(lambda _, m: bool(m.from_user and m.from_user.is_self), "MeFilter")
     """Filter messages generated by you yourself."""