README: Mention that images work with distrobox

The images should also work well with distrobox. They may not include
all the packages by default but should still reduce the setup time for
new containers via distrobox.

See: 89luca89/distrobox#544

README.md

@@ -1,9 +1,12 @@
-# Container images for toolbx
+# Container images for toolbx (and distrobox)
 
 Community maintained container images to use with [toolbx] ([GitHub]). See
 [containers/toolbox#1019] for the upstream discussion on the next steps to make
 those images more "official".
 
+You can also use them wih distrobox. See the discussion in
+[distrobox#544](https://github.com/89luca89/distrobox/issues/544).
+
 ## Available distributions and usage
 
 You can find all images in the [toolbx-images organization] on [Quay.io], or