Doc updates

[3tilley]

Proposed change

Add more information to documentation

Type of change

I've just been through the process of creating my own addon, and these are some things I've learnt and I think would help newcomers. Please check that what I have written is correct!

• [x] Document existing features within Home Assistant
• [ ] Document new or changing features which there is an existing pull request elsewhere
• [ ] Spelling or grammatical corrections, or rewording for improved clarity
• [ ] Changes to the backend of this documentation
• [ ] Removed stale or deprecated documentation

Additional information

• This PR fixes or closes issue: fixes #
• Link to relevant existing code or pull request:

[home-assistant[bot]]

Please take a look at the requested changes, and use the Ready for review button when you are done, thanks :+1:

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[3tilley]

I've made those changes, thanks for having a look!