MNT: Add template for pull request

Author: angelsevillamol

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,22 @@
+<!--
+Thanks for contributing with a pull request!
+Feel free to delete sections the template if they do not apply to the PR.
+-->
+
+#### Reference Issues/PRs
+
+<!--
+i.e. Fixes #1234 or See #3456.
+-->
+
+#### What does this implement/fix? Explain your changes
+
+<!--
+A clear and concise description of what you have implemented.
+-->
+
+#### Any other comments?
+
+<!--
+Please be aware that we are a team of volunteers so patience is necessary.
+-->