Documentation and lights.ts improvements

[tajemniktv]

PR focused on documentation, configuration clarity, and enhanced support for block-specific lighting

Documentation and Metadata:

• Added a new README.md file that introduces the Arc-3 shader pack, describes its status, installation notes, and licensing placeholder;
• Updated the _comment in shaders/pack.json to a placeholder description.

Lighting:

• Extended the ApplyLightColors function in shaders/scripts/Lights.ts to add or adjust custom light colors for several Minecraft blocks, including but not limited to: beacon, blast furnace, conduit, copper lantern variants, ender chest, end rod, furnace, lava cauldron, light block, smoker, soul fire, soul lantern, copper torch variants, and sculk catalyst.