Add pull request template

Author: vojtapol

.github/pull-request-template.md

@@ -0,0 +1,11 @@
+<!-- Uncomment one of the following lines as necessary. -->
+<!-- Fixes #<ISSUE_NUMBER> -->
+<!-- Resolves #<ISSUE_NUMBER> -->
+
+## Checklist
+<!-- Change [ ] to [x] to indicate you acknowledge the check. -->
+- [ ] Pull requests follows the [contribution guide](https://github.com/graphql-java-kickstart/graphql-java-tools/wiki/Contribution-guide)
+- [ ] New or modified functionality is covered by tests
+
+## Description
+<!-- Briefly describe how you resolved the issue or a bug. -->