Underground Rivers

• Increased the amount of glow lichen in underground rivers a bit.
• Updated to 26.1.

• Updated to 1.21.11.

• Increased glow lichen spawning in underground rivers
• Slightly increased the overall underground river size

Backport to 1.20.

Bump version numbers to support 1.21.4 and future versions.

• Bump version numbers to support 1.21.2/3

Initial release!