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/config/client.json

@@ -0,0 +1,8 @@
+{
+  "window_title": "",
+  "disable_recipe_book": false,
+  "export_atlases": false,
+  "blur_scaled_pack_icon": true,
+  "custom_stack_size_text": true,
+  "shrink_stack_size_text": true
+}