Doc changes required.

[IoTPlay]

• On flow - 3. On how it works - http endpoint is done.
• Document the effects & where to set cfg_vars
• A1c and 4b is the same thing - fix to 4b.
• Reference to HomeKit standard:
• http://auto.caitken.com/posts/2018/09/09/nodered-homekit-reference
• http://auto.caitken.com/posts/2018/09/09/nodered-homekit-characteristics-reference
• Spelling on README.md - 'iitiating'

https://github.com/IoTPlay/homedig2/blob/master/docs/1_homedig2_how.md