name relevant OSM tag values for tunnel and bridge recognition in documentation

Created by: das-g

The OSMaxx schema documentation indicates that the value of the bridge and tunnel attributes in the OSMaxx output schema depend on the OSM tags bridge=yes, bridge=no, tunnel=yes and tunnel=no, when actually, we treat bridge OSM tag values split_log, beam, culvert, low_water_crossing, yes, suspension, viaduct, aqueduct and covered as bridges and absence of the bridge tag and any other values as not a bridge. (See roads, railways, aerialways.)

The same goes for tunnes with yes/no vs. passage, culvert, noiseprotection galerie, gallery, building_passage, avalanche_protector,teilweise, viaduct, tunnel and yes.