Initial presubmit.py script.

Change-Id: I4b22f34222078ed139fca747da3f5f1733951d63
diff --git a/.gitignore b/.gitignore
index 611aac2..3fa0971 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,7 @@
 # Build artifacts
 out/
 bazel-*
+.presubmit/
 
 # IDE artifacts
 .idea/