Introduce EmptyReactNativeConfig inside Java

Summary:
I'm adding a `EmptyReactNativeConfig` for Java as we had a similar class in C++.
Ideally inside the Playbook we can allow users to use this class rather than having to
create an anonymous inner class.

Changelog:
[Internal] [Added] - Introduce EmptyReactNativeConfig inside Java

Reviewed By: ShikaSD

Differential Revision: D32277916

fbshipit-source-id: f6bbeb0477681d536dfd89930b732609add7c43a

ReactAndroid/src/main/java/com/facebook/react/fabric/EmptyReactNativeConfig.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.react.fabric;
+
+/**
+ * An empty {@link ReactNativeConfig} that is returning empty responses and false for all the
+ * requested keys.
+ */
+public class EmptyReactNativeConfig implements ReactNativeConfig {
+
+  @Override
+  public boolean getBool(final String s) {
+    return false;
+  }
+
+  @Override
+  public int getInt64(final String s) {
+    return 0;
+  }
+
+  @Override
+  public String getString(final String s) {
+    return "";
+  }
+
+  @Override
+  public double getDouble(final String s) {
+    return 0;
+  }
+}

ReactAndroid/src/main/java/com/facebook/react/fabric/ReactNativeConfig.java

@@ -10,7 +10,16 @@ package com.facebook.react.fabric;
 import androidx.annotation.NonNull;
 import com.facebook.proguard.annotations.DoNotStrip;
 
-// This is a wrapper for the ReactNativeConfig object in C++
+/**
+ * ReactNative Configuration that allows to customize the behavior of key/value pairs used by the
+ * framework to enable/disable capabilities.
+ *
+ * <p>The hosting app should provide an implementation of this interface to allow specific
+ * customization of single keys. An empty implementation is available as {@link
+ * EmptyReactNativeConfig}.
+ *
+ * <p>This is a wrapper for the ReactNativeConfig object in C++
+ */
 @DoNotStrip
 public interface ReactNativeConfig {
   /**