add a pull request template file [ci skip]

when creating a new pull request on GitHub, the pull request template file is used to provide default text for the pull request description;
must be present in the default branch (e.g. master or main) of the repository to take effect;

.github/pull_request_template.md

@@ -0,0 +1,24 @@
+<!-- Please provide a general summary of your changes in the title above. -->
+
+## Description of proposed changes
+<!-- Describe your changes in detail. -->
+
+## Types of changes
+<!-- What types of changes does your code introduce? Put an `x` in all the boxes that apply. -->
+<!-- Please try to limit your pull request to one type, submit multiple pull requests if needed. -->
+- [ ] Bugfix
+- [ ] Feature
+- [ ] Refactoring (no functional changes, no api changes)
+- [ ] Build related changes
+- [ ] Documentation updates
+- [ ] Other (please describe): 
+
+## Checklist
+<!-- Go over all the following points, and put an `x` in all the boxes that apply. -->
+- [ ] Code compiles correctly (mandatory for bugfixes / features / refactoring / build process)
+- [ ] Tests for the changes have been added / updated (mandatory for bugfixes / features)
+- [ ] Documentation has been added / updated (mandatory for bugfixes / features)
+
+## Further comments
+<!-- If this is a relatively large or complex change, kick off the discussion by explaining
+why you chose the solution you did and what alternatives you considered, etc... -->