Add AppImage topic

Author: ArqamQazi

topics/appimage/appimage.png

@@ -0,0 +1,12 @@
+---
+display_name: AppImage
+short_description: Open source format for distributing portable software on Linux.
+github_url: https://github.com/AppImage
+logo: appimage.png
+released: 2004
+topic: appimage
+url: https://appimage.org
+wikipedia_url: https://en.wikipedia.org/wiki/AppImage
+related: flatpak, linux
+---
+AppImage is an open source format for distributing portable software on Linux. It allows developers to package an application and all its dependencies into a single, self-contained file that runs on most common Linux distributions without requiring installation or root privileges.