dosemu: add screenshot and update AppImage repo link (#152)

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: andy5995

apps/dosemu.md

@@ -4,9 +4,11 @@
 
  It can also serve as a VM to boot various DOSes.
 
+ ![Screenshot](https://raw.githubusercontent.com/theimpossibleastronaut/dosemu2-appimage/44430e01afc074a72bcf62e7573322ac1c54d211/dosemu.png)
+
  SITE: https://github.com/dosemu2/dosemu2
 
- APPIMAGE: https://github.com/probonopd/doesemu2-factory
+ APPIMAGE: https://github.com/theimpossibleastronaut/dosemu2-appimage
 
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