[Docs] Document audio attachments and linked pull requests

[roomote-community]

Created by Roomote. Follow up by mentioning @roomote, in the web UI, or in Discord.

What changed

• documented audio attachment support across Slack, Discord, Microsoft Teams, and Telegram, including formats, limits, transcription behavior, and warning cases
• documented how multiple linked pull requests appear in the task view
• documented multiple active pull-request links in Slack task and automation messages

Why this change was made

Recent user-facing changes added cross-provider audio transcription and expanded linked pull-request visibility, while the public documentation still described the earlier attachment and single-PR behavior.

Impact

Users and self-hosted operators can now rely on the public docs for the shipped audio attachment requirements and understand where Roomote exposes multiple pull requests associated with one task.

Screenshots

[roomote-community]

No code issues found. See task

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