Adds three free, open-source resources to the list:

• Astroworld API to Indexes — public CORS-enabled Minecraft data API (mobs, biomes, items, enchantments, structures, commands, versions, achievements, trades).
• Astroworld Plugins to Server Plugins — seven MIT-licensed Paper plugins (AFK, MOTD, join/leave, stats, autosave, back cooldown, chatbot).
• Astroworld Tools to Web Applications — free utilities for server admins (RAM/cost calculators, MOTD generator, status checker, color pickers).

All three are free to use, no signup required, and links go to the public resources. Sticking to one PR with three additions as they all come from the same project.