Skyblock Resource Generators

Builds for Minecraft 26.1.2, 1.21.1 and 1.20.1 on Forge and NeoForge.

Guide: https://itmecasey.com/wiki/skyblock-resources/

Changes:

• Drop Terralith from the 26.1.2 NeoForge test dependencies
• Fail the CI self test after 15 minutes instead of hanging
• Accept the EULA for the CI self-test server
• Take SMWTI from the private Maven instead of a local build folder
• Resolve curse.maven dependencies from the private Maven first
• Add CI build, self test and CurseForge release workflow
• Add README with supported versions, build steps and layout
• Add issue templates for bug reports and feature requests
• Set the GitHub repository name in the branding links
• Add Skyblock Resources branding and listing copy
• Name the NeoForge 26.1.2 jar with its loader and Minecraft version like the other builds
• Fill recipe gaps: Twilight Forest, Allthemodium, Regions Unexplored and Undergarden plants, saplings that did not grow
• Fix the Oh The Biomes We've Gone sapling tag name in the version overrides
• Add recipes for the mods that have NeoForge 1.21.1 builds
• Add recipes for the 1.20.1 mods
• Add recipes for the mods that have Forge 1.21.1 builds
• Port to Forge 1.20.1
• Port to NeoForge 1.20.1
• Port to Forge 1.21.1
• Document that Forge and NeoForge are compatible only on 1.20.1