v9.0.0

• Radically optimize memory footprint and performance — on a sample 1M points index, Supercluster now uses 94% less transient allocation, 57% lower peak heap, 65% less retained memory, and runs 23% faster. #258
• Improve internal coordinate precision by 6 bits (64 times).
• ⚠️ Breaking: hard-cap maxZoom at 30 (it wasn't practical to use it on higher zooms anyway).
• Add support for MultiPoint features. #263