Add police feed

[herndlm]

I'm not sure if this one exists officially in the format needed here, but according to https://nina.api.bund.dev/ there is also a datasource / feed for police warnings.

I could not find the needed JSON feed yet, only tried guessing it based on biwapp, see

https://warnung.bund.de/api31/biwapp/mapData.json => https://warnung.bund.de/bbk.biwapp/warnmeldungen.json https://warnung.bund.de/api31/police/mapData.json => ?

Is there some place where these URLs can be extracted from? I did also not find any of those jsons while using https://warnung.bund.de/meldungen