.gitignore: add

Add .gitignore for files generated when running the gddo-server.

Change-Id: Ifaef00ef42f3fb258acf747f02eb2d7787bce941
Reviewed-on: https://go-review.googlesource.com/c/gddo/+/274695
Trust: Julie Qiu <julie@golang.org>
Run-TryBot: Julie Qiu <julie@golang.org>
Reviewed-by: Jonathan Amsterdam <jba@google.com>

.gitignore

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..0a25482
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+dump.rdb
+gddo-server/gddo-server