Essentia plugin

Basic plugin with some essential utilities and commands.

api/src/main/java/com/alttd/essentia/EssentiaAPI.java

@@ -0,0 +1,22 @@
+package com.alttd.essentia;
+
+import org.jetbrains.annotations.ApiStatus;
+
+public interface EssentiaAPI {
+
+    static EssentiaAPI get() {
+        return Provider.instance;
+    }
+
+    final class Provider {
+        private static EssentiaAPI instance = null;
+
+        @ApiStatus.Internal
+        static void register(EssentiaAPI instance) {
+            if (Provider.instance != null)
+                throw new UnsupportedOperationException("Cannot redefine singleton");
+
+            Provider.instance = instance;
+        }
+    }
+}