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

content/docs/conn_lifecycle.md

@@ -0,0 +1,42 @@
+---
+title: Connection Lifecycle
+menu: docs_architecture
+weight: 20
+---
+
+
+# Architecture overview
+
+After Server has started listening to all sockets, [`Accept`][Accept] and [`Worker`][Worker] are two main loops responsible for processing incoming client connections. 
+
+Once connection accepted Application level protocol processing happens in a protocol specific [`Dispatcher`][Dispatcher] loop spawned from [`Worker`][Worker].
+
+    Please note, below diagrams are outlining happy-path scenarios only.
+
+![](/img/diagrams/connection_overview.svg)
+
+## Accept loop in more detail
+
+![](/img/diagrams/connection_accept.svg)
+
+Most of code implementation resides in [`actix-server`][server] crate for struct [`Accept`][Accept]. 
+
+## Worker loop in more detail
+
+![](/img/diagrams/connection_worker.svg)
+
+Most of code implementation resides in [`actix-server`][server] crate for struct [`Worker`][Worker]. 
+
+## Request loop roughly
+
+![](/img/diagrams/connection_request.svg)
+
+Most of code implementation for request loop resides in [`actix-web`][web] and [`actix-http`][http] crates. 
+
+
+[server]: https://crates.io/crates/actix-server
+[web]: https://crates.io/crates/actix-web
+[http]: https://crates.io/crates/actix-http
+[Accept]: https://github.com/actix/actix-net/blob/master/actix-server/src/accept.rs
+[Worker]: https://github.com/actix/actix-net/blob/master/actix-server/src/worker.rs
+[Dispatcher]: https://github.com/actix/actix-web/blob/master/actix-http/src/h1/dispatcher.rs

content/docs/http_server_init.md

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+---
+title: Http Server Initialization
+menu: docs_architecture
+weight: 10
+---
+
+## Architecture overview
+
+Below is a diagram of HttpServer initalization, which happens on the following code
+```rust
+#[actix_rt::main]
+async fn main() -> std::io::Result<()> {
+    HttpServer::new(|| {
+        App::new()
+            .route("/", web::to(|| HttpResponse::Ok()))
+    })
+    .bind("127.0.0.1:8088")?
+    .run()
+    .await
+}
+```
+
+![](/img/diagrams/http_server.svg)