Bug 1566354 - Add an empty metrics.yaml file for streaming telemetry r=janerik

This registry file will be used for the new streaming
telemetry API used by GeckoView.

Differential Revision: https://phabricator.services.mozilla.com/D38632

--HG--
extra : moz-landing-system : lando

toolkit/components/telemetry/geckoview/streaming/metrics.yaml

@@ -0,0 +1,9 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file defines the metrics that are recorded by the Glean SDK. They are
+# automatically converted to platform-specific code at build time using the
+# `glean_parser` PyPI package.
+
+$schema: moz://mozilla.org/schemas/glean/metrics/1-0-0