Minor cleanup in README and package file (#21)

Author: dfed

Package.swift

@@ -19,7 +19,10 @@ let package = Package(
     targets: [
         .target(
             name: "AsyncQueue",
-            dependencies: []),
+            dependencies: [],
+            swiftSettings: [
+                .enableUpcomingFeature("StrictConcurrency")
+            ]),
         .testTarget(
             name: "AsyncQueueTests",
             dependencies: ["AsyncQueue"],

README.md

@@ -60,7 +60,6 @@ func testFIFOQueueOrdering() async {
             }
         }
 
-        nonisolated
         func flushQueue() async {
             await queue.enqueueAndWait { }
         }
@@ -110,7 +109,6 @@ func testActorQueueOrdering() async {
             }
         }
 
-        nonisolated
         func flushQueue() async {
             await queue.enqueueAndWait { _ in }
         }
@@ -148,7 +146,6 @@ func testMainActorQueueOrdering() async {
             }
         }
 
-        nonisolated
         func flushQueue() async {
             await MainActorQueue.shared.enqueueAndWait { }
         }