Update gitignore with PyCharm project and slash prefix

Change-Id: I78245b4c010a4809c7c3fa1f94069ec8a0d0d3aa

.gitignore

diff --git a/.gitignore b/.gitignore
index 008ed1a..93d9133 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
-release-announcement-*
+/.idea/
+/release-announcement-*