fix: add placeholder class for bigtable-stats (#1075)

* fix: add placeholder class for bigtable-stats

* fix format

Author: mutianf

google-cloud-bigtable-stats/src/main/java/com/google/cloud/bigtable/stats/MavenPlaceholderShaded.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2021 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.cloud.bigtable.stats;
+
+final class MavenPlaceholderShaded {
+  /**
+   * This class is here to force generation of source javadoc jars so that the maven release process
+   * doesn't complain. The shading plugin generated a shaded jar of bigtable-stats, but it doesn't
+   * generate javadoc or source files; this class is here as a hack and better methods should be
+   * employed.
+   */
+  private MavenPlaceholderShaded() {}
+}