Is your feature request related to a problem? Please describe.
When I share an image post from Voyager to Tusky (Mastodon client), the alt-text doesn't come along.

Describe the solution you'd like
Improving the "share" feature would solve this I suppose, but the ability to select the alt-text (and thus to copy it) would also solve the problem and sounds useful on its own as well.

Describe alternatives you've considered
I haven't found an alternative at all so far. Even opening the page in Firefox mobile doesn't let me select (or even show!) the alt-text.

Additional context
Here is a typical image post with a long alt-text I really don't want to have to type manually :
https://jlai.lu/post/22231711