OptiGUI 2.1.0 full release - Minecraft 1.20 support

[opekope2]

• Added Minecraft 1.20 support
• Added basic lectern support
• Fix #35 for good (inventory texture not updating)
• Optimize resource loader
• Merge OptiGlue 1.19.4 into 1.19.3 (which supports 1.20)