Add bibliography directive to guideline

Need to do the folowing:
- Add new directive to `conf.py`
- `generate_guidelines_template.py`
- `.github/ISSUE_TEMPLATE/CODING-GUIDELINE.yml`
- And the machinery to generate a the guideline based on the issue

Was attempted over in https://github.com/rustfoundation/safety-critical-rust-coding-guidelines/pull/300