Adding 3 Serbia layers

[stalker314314]

There are 3 layers here that we think should be used:

• Transparent layer that we use to import addresses and street on DINA (as per wiki page). This data is open and part of https://openstreetmap.org/copyright already. You can try this overlay here.
• Raster layer based on Carto of official Serbia map. This is what we offer as community, per https://openstreetmap.rs/o-mapi/. Maps comes in two scripts (they are both official in Serbia) - cyrillic and latin. You can try both of them here. That practically means:
  • including Kosovo territory as part of Serbia,
  • making name:sr (or name:sr-Latn) as default label, and
  • removing Russian version of cyrillic italic font (Serbian and Russian italic differ)

I am only not sure what to put for "available_projections" (I omitted it) - one layer is based on maptiles vector server and other is mapnik/carto raster style.