Add the dirtbike:scale=survey option

[DmitryAlexei]

Describe the idea (required)

The issue is created to discuss pull request https://github.com/osmandapp/OsmAnd-resources/pull/1087

Tell us about the expected behaviour (required)

See wiki update: https://wiki.openstreetmap.org/wiki/User:CMoffroad/Key:dirtbike:scale#How_to_map

Tell us about alternatives you've considered (required)

dirtbike:scale=survey option is added to encourage mappers to explore and document additional trails in the network

Context (optional)

No response

[cmoffroad]

I've found a workaround that eliminates the need for the additional key, so you can close this item for now. Thanks for your understanding!