Configure Gally plugin to add tax to price

[shochdoerfer]

I've encountered a minor issue with Gally in our current B2C project. The problem arises because we store prices internally as net prices, but display gross prices on the storefront.

Since Gally server only has access to the internal net prices, the price slider element appears incorrect. Unfortunately, Sylius doesn't offer a configuration option to render prices including tax, which means the Gally plugin isn't aware of our store's setup.

Should we consider adding a configuration option to the Gally plugin to accommodate this?

[shochdoerfer]

@PierreGauthier @romainruaud something to discuss :)