Stub page for Npgsql 9.0 release notes (#363)

Author: roji

conceptual/Npgsql/release-notes/9.0.md

@@ -0,0 +1,3 @@
+# Npgsql 9.0 Release Notes
+
+Nothing here yet

conceptual/Npgsql/toc.yml

@@ -2,14 +2,16 @@
   href: index.md
 - name: Release notes
   items:
+  - name: "9.0"
+    href: release-notes/9.0.md
   - name: "8.0"
     href: release-notes/8.0.md
-  - name: "7.0"
-    href: release-notes/7.0.md
   - name: "6.0"
     href: release-notes/6.0.md
   - name: Out of support
     items:
+    - name: "7.0"
+      href: release-notes/7.0.md
     - name: "5.0"
       href: release-notes/5.0.md
     - name: "4.1"