Consistent ordering and formatting for talk events

Use a consistent format for talk events, with the most recent talk at
the top of the list with the rest in a descending order.

This removes the need to use a `reverse` filter in the events partial.

source/_talks/automated-testing-lightning-talk.md

@@ -2,7 +2,8 @@
 title: Automated testing crash course
 description: A crash course in automated testing with Drupal and test-driven development (lightning talk).
 events:
-  - name: NWDUG
+  -
+    name: NWDUG
     location: Manchester, UK
     date: 2023-08-08
     url: https://www.meetup.com/nwdrupal/events/293429104