Support shadow plugin forks

Author: avaruus1

plugin-development/src/main/java/org/spongepowered/gradle/common/Constants.java

@@ -24,6 +24,10 @@
  */
 package org.spongepowered.gradle.common;
 
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
 public final class Constants {
 
     public static final String NAME = "SpongeGradle";
@@ -48,7 +52,10 @@ private Dependencies() {
     }
 
     public static final class Plugins {
-        public static final String SHADOW_PLUGIN_ID = "com.github.johnrengelman.shadow";
+        public static final List<String> SHADOW_PLUGIN_IDS = Collections.unmodifiableList(Arrays.asList(
+                "com.github.johnrengelman.shadow",
+                "io.github.goooler.shadow"
+        ));
         public static final String SHADOW_JAR_TASK_NAME = "shadowJar";
 
         private Plugins() {

plugin-development/src/main/java/org/spongepowered/gradle/plugin/SpongePluginGradle.java

@@ -279,7 +279,7 @@ public void execute(final Task a) {
 
         this.project.afterEvaluate(p -> {
             final TaskProvider<AbstractArchiveTask> archiveTask;
-            if (p.getPlugins().hasPlugin(Constants.Plugins.SHADOW_PLUGIN_ID)) {
+            if (Constants.Plugins.SHADOW_PLUGIN_IDS.stream().anyMatch(id -> p.getPlugins().hasPlugin(id))) {
                 archiveTask = p.getTasks().named(Constants.Plugins.SHADOW_JAR_TASK_NAME, AbstractArchiveTask.class);
             } else {
                 archiveTask = p.getTasks().named(JavaPlugin.JAR_TASK_NAME, AbstractArchiveTask.class);