Add “remember position” option for Local timeline

[unikitty37]

Is your feature request related to a problem? Please describe.
On smaller instances, the Local timeline is fairly manageable. But it’s a pain to have to manually scroll back to where I left off each day, because it has reset to the top on startup.

Describe the solution you'd like
There’s already an option to have the home timeline remember its position on startup; could we have the same for the Local timeline, please?

Describe alternatives you've considered
The only alternative I can think of is leaving Metatext in the foreground each time I lock my phone, in the hope that iOS won’t kill it; iOS will probably kill it anyway.

Additional context
n/a