This change updates the repository with a new Docusaurus-based
documentation website. This allows us to create our documentation using
Markdown, MDX and React. This will serve as the main entry point for
users visiting https://opendc.org. The actual OpenDC application will be
moved to https://app.opendc.org.

This change updates the project documentation by moving most of the
documentation to the docs directory.

This change merges the four main OpenDC development repositories into a
single Git repository and performs final organization of the repository.

This change prepares the simulator Git repository for the monorepo residing at
https://github.com/atlarge-research.com/opendc. To accomodate for this, we
move all files into a simulator subdirectory.

This change prepares the frontend Git repository for the monorepo
residing at https://github.com/atlarge-research.com/opendc. To
accomodate for this, we move all files into a frontend subdirectory.

This change prepares the opendc repository for a monorepo setup by
moving all files to the core/ directory. After all repositories have
been merged into this repository, we will move the correct files back.