### To update the whole environment, do the following in order:
-`niv init` will update nix/sources.nix if a new one is available
- backup your nix/sources.json: `cp nix/sources.json nix/sources.json.bak`
-`niv update` will update sources.json i.e. your version of nixpkgs used in this environment
- you may need to edit nix/android.nix if any of the attributes in there can't be found after this.
-`direnv reload` will rebuild/reload your environment (may not be necessary if it automatically reloads)
- alternatively, run `nix-shell` again (?)
-`flutter packages update` to update flutter/dart packages and get rid of the warning that you're using a different version of flutter than what was last referenced