release notes: add more recent UI changes and bugfixes

Covers darktable-org#19948, darktable-org#19949, darktable-org#20227, and darktable-org#20113.

Note the latter two bugfixes are also in 5.4.1, so not sure if they
shold be mentioned in 5.6.0 release notes.

Author: dtorop

RELEASE_NOTES.md

@@ -99,6 +99,15 @@ changes (where available).
   images from 720x450 to 1440x900. This produces better data for
   various situations, including in scopes and the color picker.
 
+- Use darktable icon in desktop environment when running under Wayland
+  on a KDE-like system. Previously the window manager would use a
+  generic icon.
+
+- Use server-side decorations (SSD) for windows when the user's window
+  manager is capable of this, to make window decorations consistent
+  with other applications. If SSD is not implemented (Gnome/Mutter
+  under Wayland), use client-side decorations (CSD).
+
 ## Performance Improvements
 
 - Increased performance for OpenCL guided filter by internal tiling.
@@ -197,6 +206,13 @@ changes (where available).
   WB. This was due to a missing reset letting the Color Calibration
   module starting with a wrong WB.
 
+- Do not cache warning icons for unreadable images. Do not show these
+  icons instead of the image if the image later is readable.
+
+- Properly initialize collection filters when darktable, on first
+  invocation, imports images from the command line. Before this fix,
+  images would disappear from lighttable view once they were brought
+  into darkroom view or when darktable was restarted.
 ## Lua
 
 ### API Version