docs: Add htop to migrated sysexts list

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: shanemcd

docs/SYSEXTS.md

@@ -15,6 +15,7 @@ We're on a journey to remove as much as possible from our bootc container image
 | `tailscale` | `tailscale` | community | ~65 MB | Available |
 | `gh` | `gh` | fedora | ~55 MB | Available |
 | `emacs` | `emacs` | fedora | ~289 MB | Available |
+| `htop` | `htop` | fedora | small | Available |
 
 ### Removed from image (no sysext)