All entities should have a 'phonetic name' attribute

In addition to a ‘display name’, each entity should have an (optional) ‘phonetic name’ so that things like TTS and Alexa/Google Assistant can correctly pronounce it.

I have a bunch of entities named for my “rec room” (short for ‘recreation’, which I pronounce ‘wreck’), and my Google Assistant (which I have set to the Aussie accent) continually reads as “reek room”. I’m sure there are others that have similar issues.

It could be used as such:

- name: recroom_tv
  display_name: "Rec room TV"
  phonetic_name: "wreck room tee vee"