Change how Dappled Forests generate to match normal forests

Currently, dappled forests require a plains biome and river to generate. A bit too often, this results in dappled forests that are either very small, very awkwardly shaped, or overall just not aesthetically pleasing. The actual biome itself is beautiful, so I was really hoping it would generate like a “traditional” forest and take up a wide space, rather than replacing another biome. As of now, it is difficult to find a dappled forest I could actually build a base in due to the aforementioned size/shape issues.