Architecture diagrams of HttpServer and Connection lifecycle (#148)

* add arch diagrams and menu

* fix colors for arch diagrams

* refine architecture diagrams, ready for review

* capitalize titles and add mmdc instruction

* apply code review requested changes

* Add links to accept, worker and dispatcher too

static/img/diagrams/connection_worker.mmd

@@ -0,0 +1,34 @@
+sequenceDiagram
+
+participant ServerBuilder
+participant WorkerClient
+participant Worker
+participant StreamService
+participant HttpServiceHandler
+participant Tokio
+
+ServerBuilder-->>Tokio: spawn(Worker)
+
+Tokio-->>Worker: poll()
+alt WorkerState::Available
+	loop
+		Worker->>WorkerClient: rx.poll_next()
+		WorkerClient->>Worker: WorkerCommand(Conn)
+		Worker->>Worker: check_readiness()
+		alt check_readiness() -> Ok(true)
+			Note over Worker,StreamService: Worker::services[Conn.token]
+			Worker-->>StreamService: call(ServerMessage::Connect(stream))
+			StreamService->>HttpServiceHandler: call(stream)
+			HttpServiceHandler->>StreamService: HttpServiceHandlerResponse as Future
+			StreamService->>Tokio: spawn(HttpServiceHandlerResponse)
+
+		else check_readiness() -> Ok(false)
+			Worker-->>Worker: WorkerState::Unavailable
+		else check_readiness() -> Err(token,idx)
+			Worker-->>Worker: WorkerState::Restarting
+		end
+	end
+end
+
+
+Note over HttpServiceHandler: process connection