Add @codesections posts

Author: codesections

raku-advent-2022/authors.md

@@ -26,4 +26,6 @@ reminders.
 11. lizmat: Rak on!
 12. jns: I'll let you know later (sic.)
 13. [terceranexus6](https://gitlab.com/terceranexus6)
+14. Sigils are an underappreciated programming technology
+15. An update on immutable data structures in Raku [won't be ready until ~Dec. 20, sorry]
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