Render players with skin

[Karang]

Add some cubes and a skin to represent the players.
Edit geometry and material here: https://github.com/PrismarineJS/prismarine-viewer/blob/master/viewer/lib/entities.js#L5

Some sources for inspiration:

• https://github.com/maxogden/minecraft-skin
• https://github.com/bs-community/skinview3d
• https://github.com/avaer/skin-js

[extremeheat]

For entity models, we can get this off of the default Bedrock resource pack.

• download: https://aka.ms/resourcepacktemplate
• github: https://github.com/ZtechNetwork/MCBVanillaResourcePack/tree/master/models

These can be automatically extracted and put into a bedrock-assets repo and referenced like minecraft-assets.

Documentation on the schema:

• https://minecraft.gamepedia.com/Tutorials/Changing_Minecraft_entity_models
• https://minecraft.gamepedia.com/Bedrock_Edition_schemas_documentation (under "geometry" section).

Existing parsers:

• https://github.com/JannisX11/blockbench/blob/master/js/io/formats/bedrock.js#L320
• https://github.com/kennyvv/Alex/blob/master/src/Alex/Graphics/Models/Entity/EntityModelRenderer.cs#L134 - Alex client also implements chests which may help solve Render chests #58