migrate to docusaurus (v2) (#266)

Co-authored-by: ibraheemdev <ibrah1440@gmail.com>

docs/http2.md

@@ -0,0 +1,38 @@
+---
+title: HTTP/2
+---
+
+import RenderCodeBlock from '@theme/CodeBlock';
+import CodeBlock from '@site/src/components/code_block.js';
+import { actixWebMajorVersion } from "@site/vars";
+
+`actix-web` automatically upgrades connections to *HTTP/2* if possible.
+
+# Negotiation
+
+<!-- TODO: use rustls example -->
+
+When either of the `rustls` or `openssl` features are enabled, `HttpServer` provides the [bind_rustls][bindrustls] method and [bind_openssl][bindopenssl] methods, respectively.
+
+<!-- DEPENDENCY -->
+
+
+<RenderCodeBlock className="language-toml">
+{`[dependencies]
+actix-web = { version = "${actixWebMajorVersion}", features = ["openssl"] }
+openssl = { version = "0.10", features = ["v110"] }
+`}
+</RenderCodeBlock>
+
+<CodeBlock example="http2" file="main.rs" section="main" />
+
+Upgrades to HTTP/2 described in [RFC 7540 §3.2][rfcsection32] are not supported. Starting HTTP/2 with prior knowledge is supported for both cleartext and TLS connections ([RFC 7540 §3.4][rfcsection34]) (when using the lower level `actix-http` service builders).
+
+> Check out [the TLS examples][examples] for concrete example.
+
+[rfcsection32]: https://httpwg.org/specs/rfc7540.html#rfc.section.3.2
+[rfcsection34]: https://httpwg.org/specs/rfc7540.html#rfc.section.3.4
+[bindrustls]: https://docs.rs/actix-web/4/actix_web/struct.HttpServer.html#method.bind_rustls
+[bindopenssl]: https://docs.rs/actix-web/4/actix_web/struct.HttpServer.html#method.bind_openssl
+[tlsalpn]: https://tools.ietf.org/html/rfc7301
+[examples]: https://github.com/actix/examples/tree/master/https-tls