QuatArg: add the conjugated() method

src/main/java/com/github/stephengold/joltjni/Quat.java

@@ -155,6 +155,17 @@ public static Quat sRotation(Vec3 axis, float angle) {
     // *************************************************************************
     // QuatArg methods
 
+    /**
+     * Return the conjugate. The current object is unaffected.
+     *
+     * @return a new object
+     */
+    @Override
+    public Quat conjugated() {
+        Quat result = new Quat(-x, -y, -z, w);
+        return result;
+    }
+
     /**
      * Return the real (W) component in single precision. The quaternion is
      * unaffected.

src/main/java/com/github/stephengold/joltjni/readonly/QuatArg.java

@@ -21,6 +21,8 @@ of this software and associated documentation files (the "Software"), to deal
  */
 package com.github.stephengold.joltjni.readonly;
 
+import com.github.stephengold.joltjni.Quat;
+
 /**
  * Read-only access to a {@code Quat}. (native type: const Quat)
  *
@@ -30,6 +32,13 @@ public interface QuatArg {
     // *************************************************************************
     // new methods exposed
 
+    /**
+     * Return the conjugate. The current object is unaffected.
+     *
+     * @return a new object
+     */
+    Quat conjugated();
+
     /**
      * Return the real (W) component in single precision. The quaternion is
      * unaffected.