🧑‍💻 Add support for custom menu and menu item fields

[Log1x]

This adds basic support for adding extra menu and menu item fields to the forms. Right now it would require you make your own migration adding the columns but another option would be to ship the plugin with a JSON column called data (for example) and adding ->statePath('data') to the Group::make()'s.

use Filament\Forms\Components\TextInput;
use Filament\Forms\Components\Toggle;
use Datlechin\FilamentMenuBuilder\FilamentMenuBuilderPlugin;

FilamentMenuBuilderPlugin::make()
    ->addMenuFields([
        Toggle::make('is_logged_in')
            ->hint('Only show this menu item when the user is logged in.'),
    ])
    ->addMenuItemFields([
        TextInput::make('classes'),
    ]);

[datlechin]

I think it's better to update the published migration or create a new migration to add the corresponding column for the custom field rather than storing the custom field in a JSON format.

And could you kindly update the README to include this?

Thank you for the PR.

[datlechin]

Thanks!