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

* chore: move guide to en folder

* docs: add english as language

docs/guide/book.toml

@@ -1,9 +1,12 @@
-[book]
+[book.en]
 title = "Dioxus Documentation"
 description = "Get started with Dioxus, a portable, performant, and ergonomic framework for building cross-platform user interfaces in Rust"
 authors = ["Jonathan Kelley"]
 language = "en"
 
+[language.en]
+name = "English"
+
 [rust]
 edition = "2018"