feat: add guide to deploying a real-time app with ppg

[ankur-arch]

Closes DA-2265

[github-actions]

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[github-actions]

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• This PR does not change any pages in a way that would require a redirect.

[github-actions]

original	preview
content/800-guides/1200-prisma-postgres-realtime-on-cloudflare.mdx	content/800-guides/1200-prisma-postgres-realtime-on-cloudflare.mdx

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Images automagically compressed by Calibre's image-actions ✨

Compression reduced images by 20.6%, saving 70.43 KB.

Filename	Before	After	Improvement	Visual comparison
static/img/guides/realtime-app-with-ppg.png	342.19 KB	271.76 KB	-20.6%	View diff

168 images did not require optimisation.

[nikolasburk]

great guide 💯 a few notes (I added these as direct comments/suggestions as well but want to emphasize them as top-level feedback too):

• when you use "sub-steps", please prefix the step with the current "top-level" step (see my comments in sections 3, 4 and 5)
• please make sure to keep indentation of code blocks in lists at 2 or 4 spaces (two should normally be enough actually)
• the real-time functionality didn't work for me; I added a Loom video with a demo in a comment

[github-actions]

Images automagically compressed by Calibre's image-actions ✨

Compression reduced images by 20.6%, saving 70.64 KB.

Filename	Before	After	Improvement	Visual comparison
static/img/guides/realtime-app-with-ppg.png	343.22 KB	272.58 KB	-20.6%	View diff

168 images did not require optimisation.

[nikolasburk]

nice work Ankur!