Added AsynchronousServerSocketChannel suspending extension functions

Closes #3

lib/src/main/kotlin/io/github/agcom/knio2/AsyncServerSocketChannel.kt

@@ -0,0 +1,17 @@
+package io.github.agcom.knio2
+
+import java.nio.channels.AsynchronousServerSocketChannel
+import java.nio.channels.AsynchronousSocketChannel
+import kotlin.coroutines.suspendCoroutine
+
+/**
+ * Suspending version of [accept][AsynchronousServerSocketChannel.accept] function.
+ *
+ * The call is not cancellable (suspends until success or failure), because the underlying channel ([AsynchronousServerSocketChannel]) provides no guarantee for cancellation.
+ * Note that closing the channel (probably) continues every call with a failure (and that covers most use cases).
+ *
+ * However, you can mimic cancellation by ignoring the call (hence, ignoring the results).
+ */
+public suspend fun AsynchronousServerSocketChannel.acceptAwait(): AsynchronousSocketChannel = suspendCoroutine {
+    accept(Unit, it.asCompletionHandler())
+}