Added 1.20.3 support

eco-api/src/main/java/com/willfp/eco/core/Prerequisite.java

@@ -37,6 +37,14 @@ public class Prerequisite {
             "Requires server to have ProtocolLib"
     );
 
+    /**
+     * Requires the server to be running 1.20.3.
+     */
+    public static final Prerequisite HAS_1_20_3 = new Prerequisite(
+            () -> ProxyConstants.NMS_VERSION.contains("20_R3"),
+            "Requires server to be running 1.20.3+"
+    );
+
     /**
      * Requires the server to be running 1.20.
      */

eco-api/src/main/java/com/willfp/eco/core/proxy/ProxyConstants.java

@@ -25,7 +25,8 @@ public final class ProxyConstants {
             "v1_19_R2",
             "v1_19_R3",
             "v1_20_R1",
-            "v1_20_R2"
+            "v1_20_R2",
+            "v1_20_R3"
     );
 
     private ProxyConstants() {