Support GET method for RESTful Switch

Add GET as a supported method for RESTful Switch.

Right now is it possible to use https://www.home-assistant.io/integrations/switch.command_line as a workaround, but will be better to use RESTful Switch

Some devices support only GET method for management. For example https://ab-log.ru/smart-house/ethernet/megad-2561

We really need that small modification. The command_line switch is not a solution for the lack of the GET method…

Another vote from me. Seems they went straight for the advanced (albeit probably correct) use case only.