Only include basic MonoBehaviour in build.

Runtime/SplineImporter.cs

@@ -9,6 +9,7 @@ using System.Collections.Generic;
 
 namespace FrameJosh.SplineImporter
 {
+#if UNITY_EDITOR
     using static SplineImporter;
     using static SplineData;
 
@@ -128,10 +129,11 @@ namespace FrameJosh.SplineImporter
             }
         }
     }
-
     [RequireComponent(typeof(SplineContainer))]
+#endif
     public class SplineImporter : MonoBehaviour
     {
+#if UNITY_EDITOR
         public TextAsset splineData;
 
         public float3 scale = new (1f, 1f, 1f);
@@ -150,8 +152,9 @@ namespace FrameJosh.SplineImporter
                 z = vector.y
             };
         }
+#endif
     }
-
+#if UNITY_EDITOR
     [Serializable]
     public class SplineData
     {
@@ -187,4 +190,5 @@ namespace FrameJosh.SplineImporter
 
         public Spline[] splines = new Spline[0];
     }
+#endif
 }