Add mixnmatch endpoint to prepare an Einakter Wikidata property #199
Description
Along the lines of the DraCor mix'n'match endpoint, we should implement one for the Einakter database, too, in order to link to our database from Wikidata. We already feature a BEACON file, which I think can be the base for this.
If we want to keep both (which I think makes sense), we could rename the BEACON file from "wikidata.txt" to "beacon.txt" and offer the mixnmatch data as "mixnmatch.csv".
Once implemented, we can start crafting the "Einakter Database" property in Wikidata.