allow passing port as argument

OFBButte.Api/Program.cs

@@ -21,10 +21,15 @@ namespace OFBButte.Api
 
         public static IWebHost CreateWebHostBuilder(string[] args)
         {
-            var host = WebHost.CreateDefaultBuilder(args)
-                .UseStartup<Startup>()
-                .UseUrls("http://localhost:29021")
-                .Build();
+            var hostBuilder = WebHost.CreateDefaultBuilder(args)
+                .UseStartup<Startup>();
+
+            if (args.Length >= 1)
+            {
+                hostBuilder.UseUrls($"http://localhost:{args[0]}");
+            }
+
+            var host = hostBuilder.Build();
 
             using(var scope = host.Services.CreateScope())
             {