chore: create pull request template (#609)

.github/pull_request_template.md

@@ -0,0 +1,19 @@
+<!--- Provide a general summary of your changes in the Title above -->
+
+## Description
+
+<!--- Describe your changes in detail -->
+
+## Related Issue(s)
+
+- #{issue number}
+
+## Verification
+
+- [ ] **Your** code builds clean without any errors or warnings
+- [ ] Manual testing done (required)
+- [ ] Relevant automated test added (if you find this hard, leave it and we'll help out)
+
+## Documentation
+
+- [ ] Documentation is updated (either in `docs`-directory, Altinnpedia or a separate linked PR in [altinn-studio-docs.](https://github.com/Altinn/altinn-studio-docs), if applicable)