imgui: mention cmake integration in release notes

nixos/doc/manual/release-notes/rl-2411.section.md

@@ -25,6 +25,8 @@
 
 ## Other Notable Changes {#sec-release-24.11-notable-changes}
 
-- Create the first release note entry in this section!
-
 <!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->
+
+- To facilitate dependency injection, the `imgui` package now builds a static archive using vcpkg' CMake rules.
+  The derivation now installs "impl" headers selectively instead of by a wildcard.
+  Use `imgui.src` if you just want to access the unpacked sources.