Clarify wording about how to load a new integration

[rccoleman]

Proposed change

Add some verbiage about the sequence of restarts and additions to load a new custom integration. I've seen two people in Discord get confused about what to add when and if/when to restart while trying to follow this simple guide.

Type of change

• [ ] Document existing features within Home Assistant
• [ ] Document new or changing features which there is an existing pull request elsewhere
• [x] 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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[frenck]

Because there hasn't been any activity on this PR for quite some time now, I've decided to close it for being stale.

Feel free to re-open this PR when you are ready to pick up work on it again 👍

../Frenck