github: add PR template

.github/pull_request_template.md

@@ -0,0 +1,25 @@
+What has been done? Why? What problem is being solved?
+
+I didn't forget about (remove if it is not applicable):
+
+- [ ] Well-written commits
+      (see [documentation][how-to-write-commit] how to write a commit message)
+- [ ] Don't forget about TarantoolBot in a commit message
+      (see [example][tarantoolbot-example])
+- [ ] Tests (see [documentation][go-testing] for a testing package)
+- [ ] Changelog (see [documentation][keepachangelog] for changelog format)
+- [ ] Documentation (see [documentation][go-doc] for documentation style guide)
+
+Related issues:
+
+Related to #XXX
+
+Part of #XXX
+
+Closes #XXX
+
+[go-doc]: https://go.dev/blog/godoc
+[go-testing]: https://pkg.go.dev/testing
+[how-to-write-commit]: https://www.tarantool.io/en/doc/latest/contributing/developer_guidelines/#how-to-write-a-commit-message
+[keepachangelog]: https://keepachangelog.com/en/1.0.0/
+[tarantoolbot-example]: https://github.com/tarantool/tt/pull/1030/commits