chore: add changelog and documentation updates

- Created a new `CHANGELOG.md` file to document all notable changes to the project, adhering to the Keep a Changelog format.
- Updated `CONTRIBUTING.md` to include instructions for building and previewing documentation using MkDocs.
- Added `mkdocs.yml` configuration for documentation generation, including navigation structure and theme settings.
- Enhanced various documentation files, including API reference, architecture overview, configuration reference, and runbook, to provide comprehensive guidance for users and developers.
- Included new sections in the README for changelog and documentation links, improving accessibility to project information.

duty_teller.egg-info/requires.txt

@@ -11,3 +11,8 @@ icalendar<6.0,>=5.0
 pytest<9.0,>=8.0
 pytest-asyncio<1.0,>=0.24
 httpx<1.0,>=0.27
+
+[docs]
+mkdocs<2,>=1.5
+mkdocstrings[python]<1,>=0.24
+mkdocs-material<10,>=9.0