add missing copyright info & reference

TerraForgedCore/src/main/java/com/terraforged/core/filter/Erosion.java

@@ -33,6 +33,35 @@ import me.dags.noise.util.NoiseUtil;
 
 import java.util.Random;
 
+/*
+ * This class in an adaption of the work by Sebastian Lague which is also licensed under MIT.
+ * Reference:
+ * https://github.com/SebLague/Hydraulic-Erosion/blob/Coding-Adventure-E01/Assets/Scripts/Erosion.cs
+ * https://github.com/SebLague/Hydraulic-Erosion/blob/Coding-Adventure-E01/LICENSE
+ *
+ * License In Full:
+ * MIT License
+ *
+ * Copyright (c) 2019 Sebastian Lague
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
 public class Erosion implements Filter {
 
     private int erosionRadius = 3;