Add initial KubeJS setup with README, configuration files, and example scripts

- Created README.txt with directory structure and usage information.
- Added common.json, client.json, and web_server.json for configuration settings.
- Introduced example server and startup scripts (main.js) for demonstration.
- Included example textures for blocks and items in the assets directory.

kubejs/README.txt

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+Find out more info on the website: https://kubejs.com/
+
+Directory information:
+
+assets - Acts as a resource pack, you can put any client resources in here, like textures, models, etc. Example: assets/kubejs/textures/item/test_item.png
+data - Acts as a datapack, you can put any server resources in here, like loot tables, functions, etc. Example: data/kubejs/loot_tables/blocks/test_block.json
+
+startup_scripts - Scripts that get loaded once during game startup - Used for adding items and other things that can only happen while the game is loading (Can be reloaded with /kubejs reload_startup_scripts, but it may not work!)
+server_scripts - Scripts that get loaded every time server resources reload - Used for modifying recipes, tags, loot tables, and handling server events (Can be reloaded with /reload)
+client_scripts - Scripts that get loaded every time client resources reload - Used for JEI events, tooltips and other client side things (Can be reloaded with F3+T)
+
+config - KubeJS config storage. This is also the only directory that scripts can access other than world directory
+exported - Data dumps like texture atlases end up here
+
+You can find type-specific logs in logs/kubejs/ directory