refactor: river (#10)

* fix: correct snowy grass block texture

* refactor: river generation

* fix: water placement error due to interpolation

* perf: improve river naturalness

* feat: add river tab item

* fix: path truncation

include/Cubed/gameplay/chunk_generator.hpp

@@ -46,6 +46,7 @@ public:
     Random& random();
     const std::array<BiomeType, 8>& neighbor_biome() const;
     void generate_cave();
+    void generate_river();
 
 private:
     static inline std::atomic<bool> is_init{false};