Update codeowners and add github PR template

Signed-off-by: Tim Smith <tsmith@chef.io>

.github/CODEOWNERS

@@ -1 +1,4 @@
-* @chef/client-maintainers
+# Order is important. The last matching pattern has the most precedence.
+
+*               @chef/client-maintainers
+.expeditor/**   @chef/jex-team

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,14 @@
+### Description
+
+[Please describe what this change achieves]
+
+### Issues Resolved
+
+[List any existing issues this PR resolves, or any Discourse or
+StackOverflow discussion that's relevant]
+
+### Check List
+
+- [ ] New functionality includes tests
+- [ ] All tests pass
+- [ ] All commits have been signed-off for the Developer Certificate of Origin. See <https://github.com/chef/chef/blob/master/CONTRIBUTING.md#developer-certification-of-origin-dco>