Add release notes for Docker and API guide

Docker developers tool and API documentation
have been added to Qinling.

Change-Id: I4a11baf2eb7177462e22270e93ff81d775c92ae2

releasenotes/notes/add-api-ref-documentation-5ec1325223ecafab.yaml

@@ -0,0 +1,10 @@
+---
+features:
+  - |
+    Add API reference documentation.
+
+    The documentation covers ``functions``, ``executions``, ``versions``,
+    ``aliases``, ``webhooks`` and ``jobs`` endpoints.
+
+    See `Qinling api-ref documentation
+    <https://developer.openstack.org/api-ref/function-engine/>`__ for details.

releasenotes/notes/add-docker-tools-cd9aa6fff8936d81.yaml

@@ -0,0 +1,13 @@
+---
+features:
+  - |
+    Docker support has been added to help people to test Qinling
+    easily and quickly. Authentication has been disabled by default
+    which means Keystone is not required.
+
+    Dockerfile has been created to build Docker image from the master branch.
+    Docker compose files have been created to deploy RabbitMQ, MySQL and
+    Qinling API/Engine containers.
+
+    Files have been added under ``tools/docker/`` directory same as for the
+    README with all the required instructions.