What does this implement/fix?

Adds a new Automations group under ESPHome Starter Kit in the sidebar, with a first tutorial: Button Controlled LEDs. The page walks readers through building an automation in the new ESPHome Device Builder GUI (no YAML by hand) so pressing the Button module toggles the RGB module.

The tutorial covers:

• Opening the editor and starting a new automation
• Setting up the trigger (Binary Sensor → On Click on the Button module) with a collapsible callout for the other button-gesture options
• Setting up the action (Light → Toggle on RGB LEDs) with an inline annotation explaining when the ID dropdown needs changing
• A collapsible YAML view of what the GUI built
• Save → Install → On the Network, plus a test step (press the button, hear the click, watch the LEDs toggle)

Effects are deliberately not covered yet because the GUI builder doesn't expose effect selection today.

mkdocs.yml changes:

• New Automations: group under ESPHome Starter Kit with the tutorial wired up
• Adds md_in_html to markdown_extensions so the <div class="annotate" markdown> annotation pattern works for inline notes inside list items (the pattern recommended by the Material annotation docs for nested content)

Screenshot placeholder for the hero image (esphome-starter-kit-button-rgb-assembled.png) is left as a <!-- TODO --> comment in the page. Will drop the image in a follow-up.

Types of changes

• Typo / wording fix
• Content update (correcting outdated info, adding missing steps, clarifications)
• New page or new product section
• Page move / rename (redirect added in mkdocs.yml)
• Image / screenshot update
• Nav / structure change
• Site config or theme change
• CI / workflows / dependencies — Does not publish

Checklist:

• This PR targets the dev branch (not main)
• Changes previewed locally with mkdocs serve
• If pages were moved or renamed, redirects were added to mkdocs.yml
• If new pages were added, nav was updated in mkdocs.yml

Summary by CodeRabbit

Release Notes

• Documentation
  • Added a new guide for creating button-controlled LED automations in ESPHome Device Builder, including step-by-step setup instructions, configuration examples, and testing steps.