Adds support for printer configuration

[valadas]

Proposed Changes

Adds support for printer configuration that grocy already supports but are not exposed in the add-on.

Related Issues

There was no issue for that, happy to create one if needed.

Summary by CodeRabbit

• New Features

  • Added options for Label Printer configuration, such as webhook URI and additional parameters.
  • Introduced Thermal Printer settings for network printer setup and receipt printing options.

• Configuration

  • Updated configuration settings to accommodate new label and thermal printer options, including flags and schema changes.

• Environment Variables

  • Added environment variables to handle label and thermal printer configurations based on user settings.