This step was necessary to move logic from CLI to lib. Indeed, the
trait returned by get_mboxes needed to implement Table, which is
related to the CLI module only.
* modified gitignore
* fixing gitignore
* reomving the himalaya.iml file
* applied cargo fmt
* adding rust-toolchain
* restoring the .gitignore file
* make nix use rust-toolchain.toml
* add back rustfmt and rust-analyzer to buildInputs
I opened an issue to see if its the correct behaviour from the
overlay: https://github.com/oxalica/rust-overlay/issues/88.
* adding clippy to rust-toolchain.toml
Co-authored-by: Clément DOUIN <clement.douin@posteo.net>