docs: renamed Anchor reference (#64)

* docs: renamed Anchor reference

* docs: updated Anchor reference

lib/game/components/flipper.dart

@@ -216,7 +216,7 @@ class Flipper extends BodyComponent with KeyboardHandler, InitialPosition {
 }
 
 /// {@template flipper_anchor}
-/// [Anchor] positioned at the end of a [Flipper].
+/// [JointAnchor] positioned at the end of a [Flipper].
 ///
 /// The end of a [Flipper] depends on its [Flipper.side].
 /// {@endtemplate}
@@ -235,7 +235,7 @@ class FlipperAnchor extends JointAnchor {
 }
 
 /// {@template flipper_anchor_revolute_joint_def}
-/// Hinges one end of [Flipper] to a [Anchor] to achieve an arc motion.
+/// Hinges one end of [Flipper] to a [FlipperAnchor] to achieve an arc motion.
 /// {@endtemplate}
 class FlipperAnchorRevoluteJointDef extends RevoluteJointDef {
   /// {@macro flipper_anchor_revolute_joint_def}