refactor: Remove the sortable_date for talks

Automatically calculate the sortable date for a talk using the event dates. This means that the `sortable_date` in the YAML front matter can be removed. Fixes #4
2021-09-08 23:47:14 +01:00 · 2021-09-08 23:47:14 +01:00 · efbd099515
commit efbd099515
parent 42e0ae1297
36 changed files with 30 additions and 34 deletions
--- a/source/_talks/drupal-8.md
+++ b/source/_talks/drupal-8.md
@ -17,7 +17,6 @@ events:
        location: Bristol, UK
        url: https://phpsw.uk
        date: 2015-04-08
-sortable_date: 2015-04-08
 ---

 This was a ten minute lightning talk, designed to highlight the major changes