add optional config path arg

[haennes]

No description provided.

[doums]

Hi, thx for this PR.
By curiosity, can you explain your use case and which custom path do you need? (Asking to see if the cli UX need more improvement other than just adding this flag).

Please, update the README to reflect the changes:

By default, bato looks for the config file `~/.config/bato/bato.toml`
(XDG_CONFIG_HOME).\
To use a custom file, run with `--config` flag.\
If the config file is not found, bato prints an error and exits.

[haennes]

I am using NixOS and would like the configuration to reside inside the /nix/store instead of just a config directory.
For most other programs this is "traditionally" solved by creating a symlink from ~/.config/bato/bato.toml to the store but i think just passing a path directly is more clean

Thanks for the quick reply :)

[doums]

Let's change this

    /// Use a custom config file
    #[arg(short = 'c', long, value_name = "FILE")]

[doums]

(see the above requests)

[haennes]

(see the above requests)

Amended them

[doums]

Looks clean, thx!