Update synfig.md

see synfig/synfig#3675

Author: ivan-hc

apps/synfig.md

@@ -1,8 +1,10 @@
 # SYNFIG
 
- Synfig Studio animation software.
+ Synfig Studio animation software. This is the unofficial AppImage.
 
- SITE/SOURCE: https://github.com/synfig/synfig
+ SITE: https://github.com/synfig/synfig
+
+ UNOFFICIAL APPIMAGE: https://github.com/BobSynfig/synfig
 
  | [Applications](https://portable-linux-apps.github.io/apps.html) | [Home](https://portable-linux-apps.github.io)
- | --- | --- |
+ | --- | --- |