Integrate modules from road-gen that are needed for segmented road generation

src/road_gen/prefabs/prefabs.py

@@ -0,0 +1,20 @@
+import numpy as np
+
+
+def straight(length: int) -> np.ndarray:
+    return np.zeros(length)
+
+
+def turn_left(length: int, radius: float) -> np.ndarray:
+    return np.full(length, 1.0 / radius)
+
+
+def turn_right(length: int, radius: float) -> np.ndarray:
+    return -turn_left(length, radius)
+
+
+PREFABS = {
+    'straight': straight,
+    'turn_left': turn_left,
+    'turn_right': turn_right,
+}