Add round temperature option to weather forecast

[flixlix]

Added option to round temperature values in the weather forecast card.

Proposed change

Added documentation for round_temperature option for weather forecast card. Related to my PR in the frontend repo: home-assistant/frontend#28103

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 logos 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: feat: round_temperature on weather forecast card frontend#28103
• Link to parent pull request in the Brands repository:
• This PR fixes or closes issue: fixes #

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.

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[Copilot]

Pull request overview

This PR adds documentation for a new round_temperature option to the weather forecast card, which allows users to round temperature values to the nearest integer. The documentation is being added to support a corresponding frontend feature.

• Adds the round_temperature configuration option to both the basic configuration section and the YAML configuration section
• Describes the option as allowing users to round all temperature values in the card to the nearest integer
• Sets the default value to false