Add support for SLR1d / SLT3d

[quantum-fc101]

@andrew-codechimp
Would you mind adding support for the SLR1d / SLT3d combi boiler?
Thanks

[andrew-codechimp]

Hi, at a quick glance I'm not seeing any difference between the SLR1c and SLR1d message wise, have you tried this integration with it?

The SLT thermostat isn't required for the integration to work so that won't make any difference.