devel-docs: update the release procedure regarding appdata contents.

devel-docs/release-howto.txt

@@ -21,14 +21,19 @@
      Mac OS and flatpak of the upcoming release so they have some time
      to sort out issues with their builds.
 
- ( ) If this is a stable release, make sure we have a <release> tag
-     inside desktop/org.gimp.GIMP.appdata.xml.in for this upcoming version.
+ ( ) Make sure we have a <release> tag inside
+     desktop/org.gimp.GIMP.appdata.xml.in for this upcoming version,
+     with type="development" for development or RC releases (set
+     type="stable", or just no type for stable releases).
+
      Some installers may feature more prominently software with recent
      releases if the appropriate tag was set (e.g. GNOME Software has a
      "Recent Releases" category).
+
      If a description is added, it may be featured in installers and
      will be translatable (use <_p> or <_li> tags to make the strings
-     localizable).
+     localizable). So it is better to prepare the description text as
+     early as possible.
 
  ( ) Wait until the date specified in the announcements, use this time
      to get bug fixes applied which don't modify strings.
@@ -62,6 +67,10 @@
          Therefore anything smaller than fullHD will look tiny and
          unsuited on a 4K or higher res display).
 
+ ( ) If ever the actual release date evolved and is different from the
+     planned date, update the "date" in the <release> tag of the appdata
+     in: desktop/org.gimp.GIMP.appdata.xml.in
+
  ( ) Bump the version number to an even micro in configure.ac and
      commit this change. It should be the version number of the
      release you are about to make. Releases always have even micro