Add pull request template (#350)

A suggested template for PRs, which could help with prompting (/
reminding) and standardising the information to be added.

Author: grega

.github/pull_request_template.md

@@ -0,0 +1,17 @@
+## Status
+
+- Closes _add issue numbers or delete_
+- Related to _add issue numbers or delete_
+
+## Points for consideration:
+
+- Security
+- Performance
+
+## What's changed?
+
+_Description of what's been done - bullets are often best_
+
+## Steps to perform after deploying to production
+
+_If the production environment requires any extra work after this PR has been deployed detail it here. This could be running a Rake task, a migration, or upgrading a Gem. That kind of thing._