Base for 4.3 work. Split Nadeko.Common into a separate project

src/Nadeko.Common/AsyncLazy.cs

@@ -0,0 +1,19 @@
+using System.Runtime.CompilerServices;
+
+namespace Nadeko.Common;
+
+public class AsyncLazy<T> : Lazy<Task<T>>
+{
+    public AsyncLazy(Func<T> valueFactory)
+        : base(() => Task.Run(valueFactory))
+    {
+    }
+
+    public AsyncLazy(Func<Task<T>> taskFactory)
+        : base(() => Task.Run(taskFactory))
+    {
+    }
+
+    public TaskAwaiter<T> GetAwaiter()
+        => Value.GetAwaiter();
+}