Internationalization: move guide to en folder and preserve its history. (#494)

* chore: move guide to en folder

* docs: add english as language

docs/guide/src/en/async/index.md

@@ -0,0 +1,9 @@
+# Working with Async
+
+Often, apps need to interact with file systems, network interfaces, hardware, or timers. This chapter provides an overview of using async code in Dioxus.
+
+## The Runtime
+
+By default, Dioxus-Desktop ships with the `Tokio` runtime and automatically sets everything up for you. This is currently not configurable, though it would be easy to write an integration for Dioxus desktop that uses a different asynchronous runtime.
+
+Dioxus is not currently thread-safe, so any async code you write does *not* need to be `Send/Sync`. That means that you can use non-thread-safe structures like `Cell`, `Rc`, and `RefCell`.