Add three autumn‑themed plants for Dappled Forest

I want to add three new autumn plants for the Dappled Forest biome: chrysanthemum, dried autumn flower, and river‑reed. They can generate naturally in this biome. These plants can be used for decoration, making yellow‑orange dyes, and can also be used as furnace fuel. They are simple static plants, no new mobs, and will not bring extra performance pressure. They enrich the autumn atmosphere of Dappled Forest and give players more building materials.