Use the test runner on the test bots for this package

BUG=
R=nweiz@google.com

Review URL: https://codereview.chromium.org//2123933002 .

pkgs/pub_semver/.test_config

diff --git a/pkgs/pub_semver/.test_config b/pkgs/pub_semver/.test_config
new file mode 100644
index 0000000..2535563
--- /dev/null
+++ b/pkgs/pub_semver/.test_config
@@ -0,0 +1,3 @@
+{
+  "test_package": true
+}