Add release notes page for v0.5.0

Patrole 0.5.0 has been released [1].
This commit adds a new page for v0.5.0 release notes.

[1] https://review.openstack.org/#/c/645868/

Change-Id: I1a75d5b57db1b6982411aace96ef9dc326d1fa90
diff --git a/releasenotes/source/index.rst b/releasenotes/source/index.rst
index eb061a4..ca4384e 100644
--- a/releasenotes/source/index.rst
+++ b/releasenotes/source/index.rst
@@ -6,6 +6,7 @@
    :maxdepth: 1
 
    unreleased
+   v0.5.0
    v0.4.0
    v0.3.0
    v0.2.0
diff --git a/releasenotes/source/v0.5.0.rst b/releasenotes/source/v0.5.0.rst
new file mode 100644
index 0000000..d806eec
--- /dev/null
+++ b/releasenotes/source/v0.5.0.rst
@@ -0,0 +1,6 @@
+====================
+v0.5.0 Release Notes
+====================
+
+.. release-notes:: 0.5.0 Release Notes
+   :version: 0.5.0