Documentation: Convert docs to markdown and improve readme

[FelixTJDietrich]

This pull request includes several updates to documentation and configuration files to improve clarity, transparency, and functionality. Key changes include enhancements to the CONTRIBUTING.md and README.md files, updates to the Sphinx documentation configuration, and minor adjustments to the Makefile.

Documentation updates:

• CONTRIBUTING.md: Added detailed contribution guidelines for both members of the organization and external contributors, emphasizing the importance of using real names and authentic profile pictures.
• README.md: Revised the project description to better reflect the mission and main features of Hephaestus, and added a new roadmap section outlining short-term, medium-term, and long-term goals.

Sphinx documentation configuration:

• docs/conf.py: Updated project metadata, added support for Markdown files with the myst_parser extension, and excluded README.md from the build process. [1] [2]

Other changes:

• docs/Makefile: Modified the --watch option to watch the entire directory instead of just the source directory.
• docs/admin/production_setup.md: Added a placeholder for production setup instructions.