Add a test for the PostgresNIO Swift client library.

It supports SNI. See discussion at
https://community.neon.tech/t/postgresnio-swift-sni-support/419/4

test_runner/pg_clients/swift/PostgresNIOExample/Sources/PostgresNIOExample/main.swift

@@ -0,0 +1,49 @@
+import Foundation
+
+import PostgresNIO
+import NIOPosix
+import Logging
+
+await Task {
+  do {
+    let eventLoopGroup = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+    let logger = Logger(label: "postgres-logger")
+
+    let env = ProcessInfo.processInfo.environment
+
+    let sslContext = try! NIOSSLContext(configuration: .makeClientConfiguration())
+
+    let config = PostgresConnection.Configuration(
+      connection: .init(
+        host: env["NEON_HOST"] ?? "",
+        port: 5432
+      ),
+      authentication: .init(
+        username: env["NEON_USER"] ?? "",
+        database: env["NEON_DATABASE"] ?? "",
+        password: env["NEON_PASSWORD"] ?? ""
+      ),
+      tls: .require(sslContext)
+    )
+
+    let connection = try await PostgresConnection.connect(
+      on: eventLoopGroup.next(),
+      configuration: config,
+      id: 1,
+      logger: logger
+    )
+
+    let rows = try await connection.query("SELECT 1 as col", logger: logger)
+    for try await (n) in rows.decode((Int).self, context: .default) {
+      print(n)
+    }
+
+    // Close your connection once done
+    try await connection.close()
+
+    // Shutdown the EventLoopGroup, once all connections are closed.
+    try eventLoopGroup.syncShutdownGracefully()
+  } catch {
+      print(error)
+  }
+}.value