A large migration of documentation over to mkdocs, and some rewrites. Some stuff (install information, basic supported systems, contributors, thanks) are still staying in README.md, and CONTRIBUTING.md is essentially duplicated right now. However, stuff like configuration and key/mouse bindings are now moved to mkdocs.
Some parts are still a bit WIP - it is definitely not done (documentation never seems to be...). However, it should be "good enough" for now, and I'm much happier working with the documentation in this form than trying to scroll through a giant endless README.md file. It also works much better for adding new documentation.
Initial refactorings and additions to support in-app config.
- Refactor our current options logic to support in-app configs. That is, we can write to a config file with our changes now.
- The default action when creating a new config file is to leave it blank. (TBD and for now, not sure on this one)
- Previously, we would set everything in a config file on startup; now we need to read from the config TOML struct whenever.
- `C` keybind is now occupied for configs.
- `no_write` option to never write to a config file.
Update dependencies to most recent versions if applicable. Refactor to deal with breaking changes. Drop MSRV due to dependency issues, just support stable and later.
