TBR: js.syncbase: Add '/.jiri' to .gitignore in all repos.

Change-Id: I9cdc73271226ddcbab7f417863ffada64bd51cea
MultiPart: 13/28
PresubmitTest: none
diff --git a/.gitignore b/.gitignore
index f3fc3c8..ad9a04d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,5 @@
+/.jiri
+#TODO(nlacasse): Get rid of .v23 below once v23->jiri transition is complete.
 /docs
 /go/bin
 /node_modules