chore: Add 0.2.9 changelog (#1025)

Author: max-sixty

CHANGELOG.md

@@ -1,20 +1,14 @@
 # PRQL Changelog
 
-## 0.2.9 — [unreleased]
+## 0.2.9 — 2022-10-14
 
-Features:
+0.2.9 is a small release containing a bug fix for empty strings.
 
 Fixes:
 
-Documentation:
-
-Web:
-
-Integrations:
-
-Internal changes:
+- Fix parsing of empty strings (@aljazerzen, #1024)
 
-## 0.2.8 — 2022-10-17
+## 0.2.8 — 2022-10-10
 
 0.2.8 is another modest release with some fixes, doc improvements, bindings
 improvements, and lots of internal changes. Note that one of the fixes causes