Add AppStream metadata

MANIFEST.in

@@ -1,4 +1,5 @@
 include chirp/share/*.desktop
+include chirp/share/*.metainfo.xml
 include chirp/share/*.png
 include chirp/share/*.svg
 include chirp/share/*.ico

chirp/share/com.chirpmyradio.CHIRP.metainfo.xml

@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<component type="desktop-application">
+  <id>com.chirpmyradio.CHIRP</id>
+  <launchable type="desktop-id">chirp.desktop</launchable>
+  <metadata_license>CC0-1.0</metadata_license>
+  <project_license>GPL-3.0-or-later</project_license>
+  <name>CHIRP</name>
+  <developer_name>CHIRP Software LLC</developer_name>
+  <summary>Program amateur radios</summary>
+  <description>
+    <p>
+      CHIRP is a free, open-source tool for programming your radio. It supports a large number of manufacturers and models,
+      as well as provides a way to interface with multiple data sources and formats.
+    </p>
+  </description>
+  <screenshots>
+    <screenshot type="default">
+      <image type="source">https://archive.chirpmyradio.com/.site/screenshot1.png</image>
+    </screenshot>
+  </screenshots>
+  <url type="homepage">https://chirpmyradio.com</url>
+  <url type="bugtracker">https://chirpmyradio.com/projects/chirp/issues</url>
+  <content_rating type="oars-1.1"/>
+</component>