Add effect service to WLED integration

[frenck]

Proposed change

Adds a wled.effect service to the WLED integration.

This allows the user to finetune the effects running on the WLED light (or set the light into a specific effect state, before turning it on.

Allows controlling:

• The effect (using an effect name or ID)
• The speed of the effect
• The intensity of the effect
• Reverse the effect

Type of change

• Spelling, grammar or other readability improvements (current branch).
• Adjusted missing or incorrect information in the current documentation (current branch).
• Added documentation for a new integration I'm adding to Home Assistant (next branch).
• Added documentation for a new feature I'm adding to Home Assistant (next branch).
• Removed stale or deprecated documentation.

Additional information

• Link to parent pull request in the codebase: Add effect service to WLED integration core#33026
• This PR fixes or closes issue:

Checklist

• This PR uses the correct branch, based on one of the following:
  • I made a change to the existing documentation and used the current branch.
  • I made a change that is related to an upcoming version of Home Assistant and used the next branch.
• The documentation follows the Home Assistant documentation standards.

[klaasnicolaas]

✅ Approved. Can be merged as soon as the parent PR gets merged 👍