Add __init__.py to make cirq.contrib.hacks a proper package (quantumlib#5662)

Co-authored-by: Tanuj Khattar <[email protected]>

Author: maffoo

Diff for: cirq/contrib/hacks/__init__.py

@@ -0,0 +1,13 @@
+# Copyright 2022 The Cirq Developers
+#
+# 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.