Better link handling (DID/handle toggle?) #3

This original social-app PR by stella3d added a preference to use DIDs instead of handles for sharing links, and Witchsky (& prior/upstream forks) uses that as the default, but for the actual url, meaning that even if you copy the current webpage address, it'll probably be longer than if it used a user's handle instead!

Adding this back as a toggle would probably make me, who likes sending/seeing nice short urls, happy, and other more functionally guided people who prefer DIDs, also maybe still happy.