[AI Gateway]: Add docs for Deepgram Workers AI Websocket models on AI Gateway for STT/TTS

[thebongy]

Summary

AI Gateway now supports proxying traffic to Deepgram models hosted on Workers AI using the realtime websocket API. This PR adds docs for the same

Documentation checklist

• Is there a changelog entry (guidelines)? If you don't add one for something awesome and new (however small) — how will our customers find out? Changelogs are automatically posted to RSS feeds, the Discord, and X.
• The documentation style guide has been adhered to.
• If a larger change - such as adding a new page- an issue has been opened in relation to any incorrect or out of date information that this PR fixes.
• Files which have changed name or location have been allocated redirects.

[github-actions]

This pull request requires reviews from CODEOWNERS as it changes files that match the following patterns:

Pattern	Owners
/src/content/docs/ai-gateway/	@abhishekkankani, @palashgo, @thebongy, @kathayl, @mchenco, @kodster28, @cloudflare/pcx-technical-writing

[github-actions]

Preview URL: https://cc03f76c.preview.developers.cloudflare.com
Preview Branch URL: https://rbansal-ai-gateway-deepgram-workers-ai-websocket.preview.developers.cloudflare.com

Files with changes (up to 15)

Original Link	Updated Link
https://developers.cloudflare.com/ai-gateway/usage/websockets-api/realtime-api/	https://rbansal-ai-gateway-deepgram-workers-ai-websocket.preview.developers.cloudflare.com/ai-gateway/usage/websockets-api/realtime-api/