message: Add an AppDescription for the Preview package
diff: <data name="AppDescriptionDev" xml:space="preserve">
  <value>The Windows Terminal, but Unofficial</value>
  </data>
  + <data name="AppDescriptionPre" xml:space="preserve">
  + <value>Windows Terminal with a preview of upcoming features</value>
  + </data>
  </root>
  \ No newline at end of file
  