Add documentation for Modbus light and fan

[vzahradnik]

Proposed change

This pull request adds documentation for new integrations, Modbus fan and Modbus light.

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).
  • I've opened up a PR to add logo's and icons in Brands repository.
• 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: Refactor Modbus switch to provide a base for other entities core#33551
• Link to parent pull request in the Brands repository:
• 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.

[frenck]

Thanks for the PR @vzahradnik!
I've reviewed it and left a couple of suggestions. Could you take a look? Thanks 👍

[vzahradnik]

@frenck thanks! I will take a look.

[vzahradnik]

@frenck, I committed all your proposed changes. Thanks for pointing them out!

[frenck]

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

[vzahradnik]

As discussed in PR home-assistant/core#33551, I will split the Fan and Light Modbus entities into two separate PRs. Therefore, I will close this PR, and will create two separate documentation PRs later.