Import models from Blockbench.

Supports most Blockbench features supported by it's built-in gltf exporter. (Also support billboards)

Future Plans

If/when Blockbench implements a CLI tool for converting a .bbmodel file to a .gltf/.glb file the plugin will be migrated to take advantage of Godot's built in .gltf/.glb importer to ensure full feature parity with Blockbench. This would have similar drawbacks to Godot's built in .blend importer where everyone who works on the project needs to have Blockbench installed.