Enable setting POI position via drag & drop on map

[svenseeberg]

Motivation

We need good way for content creators to enter location coordinates in POIs. We cannot content creators to know the difference between longitude and latitude and are capable of retrieving the numbers from a map.

WordPress currently uses Google Maps to resolve the location of an address and then display a marker on a map.

Proposed Solution

Allow dragging and dropping a marker on a map.

We have our own tile server: maps.tuerantuer.org. The style can be edited as well: https://github.com/Integreat/integreat-maplibre-style#edit-the-style

We should make use of our new UX & design expert to define a clean process for users.

[timobrembeck]

This kind of depends on #1170

[timobrembeck]

Idea: Use https://github.com/maplibre/maplibre-gl-js to render map tiles from https://maps.tuerantuer.org/ which uses the https://github.com/digitalfabrik/integreat-maplibre-style to make the preview look exactly the same as the map in the app