v3.7.0

• ⚠️ Default unit for h3_hex_area and h3_edge_length changed to kilometers
• Update h3 core library to v3.7.0
• Add h3_point_dist and h3_exact_edge_length bindings
• Add distance operator <->
• Fix h3_to_geography and h3_to_geometry refering to removed functions if extension was upgraded from pre-1.0
• Add optional input validation in geoToH3 (see #41, thanks @trylinka)
• Support unit as string argument in h3_hex_area and h3_edge_length (and flag previous version for deprecation)