refactor code into modules

src/pg_rad/objects/objects.py

@@ -0,0 +1,33 @@
+import math
+from typing import Self
+
+class Object:
+    def __init__(
+            self,
+            x: float,
+            y: float,
+            z: float,
+            name: str = "Unnamed object",
+            color: str = 'grey'):
+        """
+        A generic object.
+
+        Args:
+            x (float): X coordinate.
+            y (float): Y coordinate.
+            z (float): Z coordinate.
+            name (str, optional): Name for the object. Defaults to "Unnamed object".
+            color (str, optional): Matplotlib compatible color string. Defaults to "red".
+        """
+        
+        self.x = x
+        self.y = y
+        self.z = z
+        self.name = name
+        self.color = color
+    
+    def distance_to(self, other: Self) -> float:
+        return math.dist(
+            (self.x, self.y, self.z),
+            (other.x, other.y, other.z),
+        )