feat: Working on hummingbird app

Sources/HApp/App.swift

@@ -0,0 +1,29 @@
+import ArgumentParser
+import Hummingbird
+import Logging
+
+@main
+struct App: AsyncParsableCommand {
+
+  @Option(name: .shortAndLong)
+  var hostname: String = "127.0.0.1"
+
+  @Option(name: .shortAndLong)
+  var port: Int = 8080
+
+  @Option(name: .shortAndLong)
+  var logLevel: Logger.Level?
+
+  func run() async throws {
+    let app = try await buildApplication(.init(hostname: hostname, port: port, logLevel: logLevel))
+    try await app.runService()
+  }
+}
+
+/// Extend `Logger.Level` so it can be used as an argument
+
+#if hasFeature(RetroactiveAttribute)
+  extension Logger.Level: @retroactive ExpressibleByArgument {}
+#else
+  extension Logger.Level: ExpressibleByArgument {}
+#endif