Update book.toml

Author: orzklv

rustbook-uz/book.toml

@@ -7,3 +7,4 @@ additional-css = ["ferris.css", "theme/2018-edition.css"]
 additional-js = ["ferris.js"]
 git-repository-url = "https://github.com/rust-lang-uz/book"
 site-url = "/book/"
+use-site-url-as-root = true