Add FAQ for generating SRT/VTT captions with speaker labels

[devin-ai-integration]

Summary

Adds a new FAQ page explaining how to generate SRT or VTT caption files that include speaker labels. The export captions endpoint doesn't include speaker information by default, but users can build custom caption files using the transcript JSON response with Speaker Diarization enabled.

Changes:

• Created new FAQ page at fern/pages/faq/async/is-there-a-way-to-generate-srt-or-vtt-captions-with-speaker-labels.mdx
• Added the FAQ to the navigation in fern/docs.yml (placed after the related "Does it cost extra to export SRT or VTT captions?" FAQ)
• Added an "Additional resources" section to the Export SRT/VTT Caption Files page linking to the new FAQ

Review & Testing Checklist for Human

• Verify the cookbook link /docs/guides/speaker_labelled_subtitles resolves correctly to the "Create Subtitles with Speaker Labels" cookbook
• Verify the API reference link /docs/api-reference/transcripts/get-subtitles is correct
• Check that the FAQ content accurately describes the workaround for generating captions with speaker labels

Notes

Based on information from Pylon Knowledge Base article (not linked per request).

Link to Devin run: https://app.devin.ai/sessions/52ea3aa15b5b413d8697e04d141403ad
Requested by: Lee Vaughn (@LeeVaughn)

[devin-ai-integration]

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