Add pull request template

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,31 @@
+<!--
+Thank you very much for contributing code or documentation to restic! Please
+fill out the following questions to make it easier for us to review your
+changes.
+
+You do not need to check all the boxes below all at once, feel free to take
+your time and add more commits. If you're done and ready for review, please
+check the last box.
+-->
+
+### What is the purpose of this change? What does it change?
+
+<!--
+Describe the changes here, as detailed as needed.
+-->
+
+### Was the change discussed in an issue or in the forum before?
+
+<!--
+Link issues and relevant forum posts here.
+-->
+
+### Checklist
+
+- [ ] I have read the [Contribution Guidelines](https://github.com/restic/restic/blob/master/CONTRIBUTING.md#providing-patches)
+- [ ] I have added tests for all changes in this PR
+- [ ] I have added documentation for the changes (in the manual)
+- [ ] There's an entry in the `CHANGELOG.md` file that describe the changes for our users
+- [ ] I have run `gofmt` on the code in all commits
+- [ ] All commit messages are formatted in the same style as [the other commits in the repo](https://github.com/restic/restic/blob/master/CONTRIBUTING.md#git-commits)
+- [ ] I'm done, this Pull Request is ready for review