mner: Montenegro regional roads

[panda80]

MNE R6
Add also the small section between the 2 border crossings with Serbia to HB

MNE R8
Add a WP in Grahovo

MNE R9
Seems to go to the Kosovo border

MNE R15
M1 is off

MNE R23
Add a WP close to the north end in Bogetici (the road there gives access to the Ostrog Monastery, and I need that WP – during this travel-free time I am happy for every m of new Mileage 😊 )

The other ones are fine.

[michih]

Activation with next site update: https://github.com/TravelMapping/HighwayData/pull/3822