Reimplementation and expansion of the Rainforest as a new biome.

Body:

The Rainforest biome, originally present in Java Edition Alpha v1.2.0, should be re-implemented with updated characteristics that fill an ecological gap between jungle and forest biomes.

Proposed features:

• Warm, humid climate with dense vegetation and an intense emerald-green grass color with a slightly dark, bluish tint
• Natural generation of small lakes, rivers, and bamboo clusters
• No dead leaf coverage on the ground
• Oak trees as the dominant tree type, alongside small shrubs (a single oak log surrounded by leaves), similar to jungle bush generation
• Biome size comparable to regular oak forests, with flatter terrain near sea level at the edges and elevated, hilly terrain at the center
• Proximity generation near: mountains, cherry groves, forests, and bamboo jungles

Mob spawns:

Foxes, cows, sheep, pigs, and wolves would spawn here, all using warm-climate variant skins. Wolves would feature a unique skin inspired by the extinct Japanese wolf (Canis lupus hodophilax). Pandas, ocelots, parrots, and jungle wolves would NOT spawn in this biome.

This biome would serve as a natural transition zone, offering a visually distinct and ecologically coherent environment that currently has no equivalent in the game.