[docs] Add typing info to quick start (#1082)

* [docs] Add typing info to quick start

ref: #982

* Add to authors (including fixing ordering)

* Fix base module --> api

* Update docs/source/quickstart.rst

---------

Co-authored-by: Mickaël Schoentgen <contact@tiger-222.fr>

docs/source/quickstart.rst

@@ -52,3 +52,22 @@ file system changes and simply print them to the console::
         observer.join()
 
 To stop the program, press Control-C.
+
+Typing
+------
+If you are using type annotations it is important to note that
+`watchdog.observers.Observer` is not actually a class; it is a variable that
+hold the "best" observer class available on your platform.
+
+In order to correctly type your own code your should use
+`watchdog.observers.api.BaseObserver`. For example:
+
+    from watchdog.observers import Observer
+    from watchdog.observers.api import BaseObserver
+
+    def my_func(obs: BaseObserver) -> None:
+        # Do something with obs
+        pass
+
+    observer: BaseObserver = Observer()
+    my_func(observer)