Update pull_request_template.md (#127)

add a link to design documentation

.github/pull_request_template.md

@@ -1,7 +1,7 @@
 ## Requirements
 
 - [ ] This PR has a title that briefly describes the work done, including the ticket number if there is a ticket.
-- [ ] My work conforms to the [**OpenMRS 3.0 Styleguide**](https://om.rs/styleguide).
+- [ ]  My work conforms to the [**OpenMRS 3.0 Styleguide**](https://om.rs/styleguide) and [**design documentation**](https://zeroheight.com/23a080e38/p/880723-introduction).
 - [ ] I checked for feature overlap with [**existing widgets**](https://om.rs/directory).