Fix appstream data to make flatpak/flathub happy

1. icon seems to be not working for flatpak build
2. add more urls and fix the out-of-date url
3. add developer
4. add oras tag

Author: wengxt

org.fcitx.Fcitx5.Addon.Cskk.metainfo.xml.in

@@ -5,10 +5,14 @@
   <metadata_license>CC0-1.0</metadata_license>
   <project_license>GPL-3.0+</project_license>
   <name>fcitx5-cskk</name>
-  <icon type="cached">cskk.png</icon>
   <summary>libCSKK Japanese input method</summary>
-  <url type="homepage">https://github.com/naokiri/fcitx5-cskk</url>
-  <url type="bugtracker">https://github.com/naokiri/fcitx5-cskk/issues</url>
+  <developer id="org.fcitx-im">
+      <name>The Fcitx Team</name>
+      <name>Naoaki Iwakiri</name>
+  </developer>
+  <url type="homepage">https://github.com/fcitx/fcitx5-cskk</url>
+  <url type="bugtracker">https://github.com/fcitx/fcitx5-cskk/issues</url>
+  <url type="vcs-browser">https://github.com/fcitx/fcitx5-cskk</url>
   <project_group>Fcitx</project_group>
   <releases>
     <release version="1.2.0" date="2023-02-05"/>