add support for toml config.

subject module added, supports callbacks.

events module added. Provides an event listener and callback trigger.

import isorted, code run through black.

toml section added to readme.

added a couple of examples.

examples/events/__main__.py

@@ -0,0 +1,26 @@
+import obsstudio_sdk as obs
+
+
+class Observer:
+    def __init__(self, cl):
+        self._cl = cl
+        self._cl.callback.register(
+            [self.on_current_program_scene_changed, self.on_exit_started]
+        )
+        print(f"Registered events: {self._cl.callback.get()}")
+
+    def on_exit_started(self):
+        print(f"OBS closing!")
+        self._cl.unsubscribe()
+
+    def on_current_program_scene_changed(self, data):
+        print(f"Switched to scene {data['sceneName']}")
+
+
+if __name__ == "__main__":
+    cl = obs.EventsClient()
+    observer = Observer(cl)
+
+    while cmd := input("<Enter> to exit\n"):
+        if not cmd:
+            break