Add perma copyable IDs/perma links to pages

[lehkost]

After the implementation of IDs for both German plays and originals (see #125), we should have copyable perma links just like on main DraCor. They could be realised either right next to the main title at the top of a page, or as a normal data field at the bottom.

Examples for perma links:
https://einakter.staging.dracor.org/id/ein001153 (German one-act play)
https://einakter.staging.dracor.org/id/eorig000025 (original)

I propose an iconic link using the letters "EIN" from our logo.