README.md - Add note to access frontend UI

[baylanger]

I'm creating this PR simply because I wasn't sure if the adaptive_lighting: entry is a requirement to access the UI. The old Configuration -> Integrations now named Settings -> Devices & Services confused me.

After reading this below, I'm unclear if it's possible to add configuration entries in the YAML and others via the UI. I'm used to see integrations either use either YAML or UI but never both at the same time. Per the wordings, it seems like it's possible to use both at the same time but likely making sure there's no collision, i.e. 2 identical names.

Configure an Adaptive Lighting component. Option names align with the YAML settings. If you've defined this entry in YAML, no options will appear here. For interactive graphs that demonstrate parameter effects, visit [this web app](https://basnijholt.github.io/adaptive-lighting). For further details, see the [official documentation](https://github.com/basnijholt/adaptive-lighting#readme).

Per any comments, the wording will probably need some adjustments but feel free to close this PR and make the proposed changes via another one.

[basnijholt]

It's possible to have both yes.

Thanks for fixing this!

@all-contributors please add @baylanger for docs

[allcontributors]

@basnijholt

I couldn't determine any contributions to add, did you specify any contributions?
Please make sure to use valid contribution names.

I've put up a pull request to add @baylanger! 🎉