add basic support for mypy type checking

bumble/transport/emulated_bluetooth_vhci_pb2.pyi

@@ -0,0 +1,19 @@
+# Copyright 2021-2023 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.
+
+import emulated_bluetooth_packets_pb2 as _emulated_bluetooth_packets_pb2
+from google.protobuf import descriptor as _descriptor
+from typing import ClassVar as _ClassVar
+
+DESCRIPTOR: _descriptor.FileDescriptor