Add to MethodSpec javadoc methods for @return tag

[coe-nathan]

For sample code below, I would expect the output to have a place to include documentation for a return value. Nothing currently exists.

public static void main(String[] args) {
    MethodSpec ms = MethodSpec.methodBuilder("methodName")
        .addParameter(ParameterSpec.builder(String.class, "str").addJavadoc("foo").build())
        .addParameter(ParameterSpec.builder(int.class, "num").addJavadoc("bar").build())
        .addJavadoc("@return output")
        .returns(String.class)
        .addStatement("return $S", "baz")
        .build();
    String text = ms.toString();
    System.err.println(text);
}

Current method generation

/**
 * @return output
 * @param str foo@param num bar
 */
java.lang.String methodName(java.lang.String str, int num) {
  return "baz";
}

Desired method generation

/**
 * @param str foo@param num bar
 * @return output
 */
java.lang.String methodName(java.lang.String str, int num) {
  return "baz";
}