add appstream file to kruler

this is necessary to get kruler to appear in appstream-driven software
stores.

REVIEW: 129322

CMakeLists.txt

@@ -66,6 +66,7 @@ install(TARGETS kruler ${KDE_INSTALL_TARGETS_DEFAULT_ARGS})
 ########### install files ###############
 
 install( PROGRAMS org.kde.kruler.desktop  DESTINATION  ${KDE_INSTALL_APPDIR} )
+install( FILES org.kde.kruler.appdata.xml    DESTINATION  ${KDE_INSTALL_METAINFODIR} )
 install( FILES kruler.notifyrc  DESTINATION  ${KDE_INSTALL_KNOTIFY5RCDIR} )
 install( FILES move.wav  DESTINATION  ${KDE_INSTALL_DATADIR}/kruler/sounds )
 feature_summary(WHAT ALL INCLUDE_QUIET_PACKAGES FATAL_ON_MISSING_REQUIRED_PACKAGES)

org.kde.kruler.appdata.xml

+<?xml version="1.0" encoding="utf-8"?>
+<component type="desktop">
+  <id>org.kde.kruler.desktop</id>
+  <metadata_license>CC0-1.0</metadata_license>
+  <project_license>GPL-2.0+</project_license>
+  <name>KRuler</name>
+  <summary>Screen Ruler</summary>
+  <description>
+    <p>KRuler is an on-screen ruler for measuring pixels. Position the 0 at your starting point and measure the precise pixel distance between the starting point and your cursor.</p>
+  </description>
+  <url type="homepage">https://www.kde.org/applications/graphics/kruler/</url>
+  <url type="bugtracker">https://bugs.kde.org/enter_bug.cgi?product=kruler</url>
+  <url type="donation">https://www.kde.org/community/donations</url>
+  <provides>
+    <binary>kruler</binary>
+  </provides>
+  <project_group>KDE</project_group>
+</component>