Add donation link to appear on Nextcloud appstore

[vitormattos]

Description

For better visibility to users (who will not visit github page)

For preview of result see for example https://apps.nextcloud.com/apps/passwords

URL copied from "Sponsor this project" section.

Describe alternatives you've considered

Also would be good to add Strype link:

#5098 (comment)

Additional context

This issue is open to contributors. If you're interested, feel free to leave a comment or open a draft PR to get started!