Update community forum link (#3601)

The community forum now has a dedicated nginx gateway fabric page.

Author: sjberman

CONTRIBUTING.md

@@ -25,8 +25,7 @@ considering contributing!
 
 To ask a question, use [Github Discussions](https://github.com/nginx/nginx-gateway-fabric/discussions).
 
-[NGINX Community Slack](https://community.nginx.org/joinslack) has a dedicated channel for this
-project -- `#nginx-gateway-fabric`.
+[NGINX Community Forum](https://community.nginx.org/c/projects/nginx-gateway-fabric/25).
 
 Reserve GitHub issues for feature requests and bugs rather than general questions.
 

README.md

@@ -4,7 +4,7 @@
 [![Go Report Card](https://goreportcard.com/badge/github.com/nginx/nginx-gateway-fabric)](https://goreportcard.com/report/github.com/nginx/nginx-gateway-fabric)
 [![codecov](https://codecov.io/gh/nginx/nginx-gateway-fabric/graph/badge.svg?token=32ULC8F13Z)](https://codecov.io/gh/nginx/nginx-gateway-fabric)
 [![GitHub release (latest SemVer)](https://img.shields.io/github/v/release/nginx/nginx-gateway-fabric?logo=github&sort=semver)](https://github.com/nginx/nginx-gateway-fabric/releases/latest)
-[![Forum](https://img.shields.io/badge/nginx--community--forum-green)](https://community.nginx.org/)
+[![Forum](https://img.shields.io/badge/nginx--community--forum-green)](https://community.nginx.org/c/projects/nginx-gateway-fabric/25)
 [![Project Status: Active – The project has reached a stable, usable state and is being actively developed.](https://www.repostatus.org/badges/latest/active.svg)](https://www.repostatus.org/#active)
 
 # NGINX Gateway Fabric
@@ -118,7 +118,7 @@ contact us directly on the [NGINX Community Forum][forum].
 
 [bug]: https://github.com/nginx/nginx-gateway-fabric/issues/new?assignees=&labels=&projects=&template=bug_report.md&title=
 [idea]: https://github.com/nginx/nginx-gateway-fabric/discussions/categories/ideas
-[forum]: https://community.nginx.org/
+[forum]: https://community.nginx.org/c/projects/nginx-gateway-fabric/25
 
 ## Community Meetings