Update README for new Cloud functions, and tighter deviceid error checking

[uzlonewolf]

README update as requested in #219, and a bit tighter error checking for the deviceid arguments.

[jasonacox]

Thank you!

Off topic a bit, but you got me thinking about expanding Cloud functions, should we expose short-cut lookup functions as well? I'm thinking about getname(id) getkey(id) getmac(id) etc. (though things like product_name and icon could be helpful or useless). All of this can be derived from getdevices() payload today, but wondering if these functions could be useful.

[uzlonewolf]

I'm not feeling functions for stuff that's available from getdevices(), you just know someone is going to do something stupid and make a new request for every attribute for every device, and I'd rather not give Tuya a reason to restrict API access. If it's for something not available from getdevices() then sure, but with the sheer number of possible API calls I would only add them for things which would be rather useful (such as the device logs) or if we get a request for it.

[uzlonewolf]

Oh, and Happy Thanksgiving!

[jasonacox]

Thanks @uzlonewolf !! Happy Thanksgiving to you too! 🙏