fix: DH-23199: Add overload function

plugin/src/main/java/io/deephaven/plugin/js/JsPlugin.java

@@ -108,7 +108,10 @@
      *
      * @return the loader configuration
      */
-    public abstract Optional<Object> loader();
+    @Default
+    public Optional<Object> loader() {
+        return Optional.empty();
+    }
 
     @Override
     public final <T, V extends Plugin.Visitor<T>> T walk(V visitor) {

server/src/main/java/io/deephaven/server/plugin/js/JsPluginManifestEntry.java

@@ -28,6 +28,14 @@ public static Builder builder() {
         return ImmutableJsPluginManifestEntry.builder();
     }
 
+    @JsonCreator
+    public static JsPluginManifestEntry of(
+            @JsonProperty(value = NAME, required = true) String name,
+            @JsonProperty(value = VERSION, required = true) String version,
+            @JsonProperty(value = MAIN, required = true) String main) {
+        return JsPluginManifestEntry.of(name, version, main, null);
+    }
+
     @JsonCreator
     public static JsPluginManifestEntry of(
             @JsonProperty(value = NAME, required = true) String name,