Add blog post for entry.runtime_data

[cdce8p]

Proposed change

Blog post for entry.runtime_data implemented in home-assistant/core#115669.
/CC @frenck

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:

[joostlek]

One thing I was also wondering, currently we don't want people to touch hass.data in tests. Is this going to be the same with runtime data?

[frenck]

One thing I was also wondering, currently we don't want people to touch hass.data in tests. Is this going to be the same with runtime data?

The use is the same on both. It is merely the location is different.

[frenck]

Thanks, @cdce8p 👍

../Frenck

[epenet]

Reading this, I wasn't sure how to check if services should be registered and de-registered.
Should there be note to use this?

        loaded_entries: list[MyConfigEntry] = [
            entry
            for entry in hass.config_entries.async_entries(DOMAIN)
            if entry.state == ConfigEntryState.LOADED
        ]

(spotted in home-assistant/core#116454)