Update docs for select selector

[raman325]

Proposed change

Adocumenting the following new config options for the select selector from home-assistant/frontend#12099 :

• multiple: Allows the user to select multiple items from the list
• mode: list forces a radio button list, dropdown forces a dropdown, nothing lets the frontend decide
• custom_value: Allows users to enter custom values into the selector

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: Add support for new select selector properties core#68952
• 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.

[frenck]

Thanks, @raman325 👍

comment addressed