docs: mention Symfony Notifier integration

[vjymisal0]

Summary

• add the Symfony Notifier for Novu community integration to the README

Closes #3632

Validation

• git diff --check
• gh repo view symfony/novu-notifier --json nameWithOwner,url

Greptile Summary

The PR documents the community-maintained Symfony Notifier integration in the root README.

• Adds a Community integrations section.
• Links to the official Symfony Novu Notifier repository and briefly describes its purpose.

Confidence Score: 5/5

The documentation-only change appears safe to merge.

The new link targets the canonical Symfony Novu Notifier repository, its description matches the integration’s purpose, and no repository documentation convention or automated README generation contract is violated.

Important Files Changed

Filename	Overview
README.md	Adds an accurate link and description for the Symfony Notifier community integration; no issues identified.

_{Reviews (1): Last reviewed commit: "docs: mention Symfony Notifier integrati..." | Re-trigger Greptile}

[netlify]

👷 Deploy request for dashboard-v2-novu-staging pending review.

Visit the deploys page to approve it

Name	Link
🔨 Latest commit	4797968

[vercel]

@vjymisal0 is attempting to deploy a commit to the Novu Team on Vercel.

A member of the Team first needs to authorize it.

[vjymisal0]

The only red check is the Vercel deploy authorization for an external contributor. The docs change itself is approved; this needs someone from the Novu Vercel team to authorize or rerun the preview.