add: grpc cf tunnel docs (#18850)

Author: devarshishimpi

src/content/docs/cloudflare-one/connections/connect-networks/use-cases/index.mdx

@@ -12,3 +12,4 @@ Cloudflare Tunnel creates a secure, outbound-only connection between your servic
 * [SSH](/cloudflare-one/connections/connect-networks/use-cases/ssh/)
 * [RDP](/cloudflare-one/connections/connect-networks/use-cases/rdp/)
 * [SMB](/cloudflare-one/connections/connect-networks/use-cases/smb/)
+* [gRPC](/cloudflare-one/connections/connect-networks/use-cases/grpc/)