docs/release-notes: update for release 0.26.0

Author: prestist

docs/release-notes.md

@@ -4,7 +4,20 @@ nav_order: 8
 
 # Release notes
 
-## Upcoming coreos-installer 0.26.0 (unreleased)
+## Upcoming coreos-installer 0.27.0 (unreleased)
+
+Major changes:
+
+
+Minor changes:
+
+
+Internal changes:
+
+
+Packaging changes:
+
+## Upcoming coreos-installer 0.26.0 (2026-02-27)
 
 Major changes:
 
@@ -18,8 +31,6 @@ Internal changes:
 
 - install: Simplify firstboot-args handling in config file expansion
 
-Packaging changes:
-
 ## coreos-installer 0.25.0 (2025-09-29)
 
 Major changes: