Added "Minecraft Image to Blocks Model" plugin.

[MarkusBordihn]

Added "Minecraft Image to Blocks Model" plugin.

For more details, see: https://github.com/MarkusBordihn/blockbench-plugins/blob/master/plugins/minecraft_image_to_blocks/about.md

[JannisX11]

Reviewed the plugin today:

• Undo integration seems to be missing. Importing a PNG, then pressing Undo does not work correctly.
• I noticed that when importing two images of different sizes, the image that was imported first becomes invisible
• Especially if this is intended for the Java block/item format, larger images can generate beyond the 48x48x48 pixel limit, which can result in users having issues when they want to continue editing the model.
• The plugin failed to load in the web app. Consider supporting the web app or setting it to desktop-only.

Correct me if I'm wrong, but generally the only functionality this seems to offer over the built-in Import > Extruded Texture is generating based on pixel color. Which isn't necessarily a blocker, but something to consider.