Add intro

docs/developer/explanations/events.rst

@@ -1,6 +1,11 @@
 Events Emitted by the Worker
 ============================
 
+Blueapi adds new events on top of the `bluesky event model`_.
+
+Reasons
+-------
+
 Since the ``RunEngine`` is traditionally used by a human in front of an IPython terminal, it
 sometimes assumes intuitive behavoir. The worker replaces the human and so must fill in the
 gaps.
@@ -59,4 +64,4 @@ ActiveMQ will give this header a different name depending on the protocol you us
 
 .. _`bluesky event model`: https://blueskyproject.io/event-model/main/index.html
 .. _`run start document`: https://blueskyproject.io/event-model/main/user/explanations/data-model.html#run-start-document
-.. _`Microsoft Playbook on Correlation IDs`: https://microsoft.github.io/code-with-engineering-playbook/observability/correlation-id/
+.. _`Microsoft Playbook on Correlation IDs`: https://microsoft.github.io/code-with-engineering-playbook/observability/correlation-id/