Ignore generated release announcement files

Change-Id: Idae2a7b07e02322665369adebde94391b4cab87c
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..008ed1a
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+release-announcement-*