Put pull request template prose in comment

Author: killercup

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,7 +1,11 @@
+<!--
 Thank you for taking the time to contribute to this project!
 
-To ease reviewing your changes and making sure we don't forget anything,
-please take a minute to check the following (remove lines that don't apply):
+To ease reviewing your changes and making sure we don't forget anything,  please
+take a minute to check the following (remove lines that don't apply), and
+replace this text with a description of what this PR does. Bonus points for
+linking to issues! :)
+-->
 
 - [ ] I have created tests for any new feature, or added regression tests for bugfixes.
 - [ ] `cargo test` succeeds