Add Locations, Geocoding and prepare Google Maps embedding

[mediafinger]

Idea

The Location model should contain some information that allows to identify a place and ideally display it on a map.

To help with this - and to have sanitized addresses - Geocoding will be used.

TODOs

• [ ] compare Location attributes with other open branch
  • https://github.com/mediafinger/yournaling/compare/main...add-memories
• [ ] decide which Location attributes to implement
• [ ] decide how complex or simple the logic should be
• [ ] write specs to all the (reverse) geocoding options
• [ ] test google maps embed

[mediafinger]

Closed after the implementation of Locations, Geocoding and Maps display has been done in:

• https://github.com/mediafinger/yournaling/pull/24
• https://github.com/mediafinger/yournaling/pull/31
• https://github.com/mediafinger/yournaling/pull/34