Ability to adjust what part of an image will be highlighted in the preview

[GrahamDo]

On the official web app, before you post a toot containing an image, you can choose to Edit that image and adjust the spotlight to tell Mastodon where to place its focus when generating the square preview in timelines (see screenshot attached).

I thought that was really cool and unique, and I'd like to be able to do that in Sengi too. :-)