Add codenotary to add-on config.yaml documentation

[ikifar2012]

Proposed change

After attempting to setup codenotary signatures for my addons I followed the documentation, only to realise after looking at other addons, I required the codenotary option along with an email in the config.yaml which was not documented

Type of change

• 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:

[frenck]

Thanks, @ikifar2012 👍