Add pull request template

.github/pull_request_template.md

@@ -0,0 +1,14 @@
+Thanks for your contribution! To make sure everything is in place, please check the instructions below.
+If anything is unclear or does not work, don't hestitate to submit the PR as is.
+
+1. If the changes warrant a release (if in doubt, assume yes), bump the version numbers of the affected packages.
+   The version number is of the format `YYYY.MM-NN`, where `YYYY` and `MM` are the current year and month, and `NN` is a two digit number counting upwards, starting from `01` each month.
+2. Look for warnings of the following format when loading packages:
+   ```
+   WARNING: The file <file> in package <package> differs from the automatically generated one.
+   You can view the automatically generated file at the following path: <tmp_path>
+   ```
+   If such a warning appears, copy the file at `<tmp_path>` to `<file>` in package `<package>`.
+3. Run `FreydCategoriesForCAP/examples/generate_documentation.g` to update the documentation.
+4. Execute `make test` in `CompilerForCAP` to update the precompiled code.
+5. Add and commit all files changed by the steps above.