cockpit/metainfo: add basic metainfo file

This is almost a straight copy from the cockpit-composer repo.

cockpit/public/org.image-builder.cockpit-image-builder.metainfo.xml

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<component type="addon">
+  <id>org.image-builder.cockpit-image-builder</id>
+  <metadata_license>CC0-1.0</metadata_license>
+  <name>Image Builder</name>
+  <summary>
+      Build customized operating system images
+  </summary>
+  <description>
+    <p>
+      Image Builder can generate custom images suitable for deploying
+      systems, or as images ready to upload to the cloud.
+    </p>
+  </description>
+  <extends>org.cockpit_project.cockpit</extends>
+  <url type="homepage">https://github.com/osbuild/image-builder-frontend/</url>
+  <launchable type="cockpit-manifest">cockpit-image-builder</launchable>
+</component>