add PR template

.github/pull_request_template.md

@@ -0,0 +1,8 @@
+- **PR Description**
+
+- **Please check if the PR fulfills these requirements**
+
+* [ ] Cheatsheets are up-to-date (run `go run scripts/cheatsheet/main.go generate` if not)
+* [ ] Code has been formatted (run `go install mvdan.cc/gofumpt@latest && gofumpt -l -w .`)
+* [ ] Tests have been added/updated (see [here](https://github.com/jesseduffield/lazygit/blob/master/pkg/integration/README.md) for the integration test guide)
+* [ ] docs (specifically `docs/Config.md`) have been updated if necessary