Update Rust documentation (1.58.1)

assets/stylesheets/pages/_rust.scss

@@ -2,6 +2,7 @@
   @extend %simple;
 
   h4 { @extend %block-label; }
+  .code-header { @extend %code; }
   .docblock { margin-left: 1em; }
   div.information, div.important-traits {
     @extend %note;

lib/docs/scrapers/rust.rb

@@ -3,7 +3,7 @@
 module Docs
   class Rust < UrlScraper
     self.type = 'rust'
-    self.release = '1.57.0'
+    self.release = '1.58.1'
     self.base_url = 'https://doc.rust-lang.org/'
     self.root_path = 'book/index.html'
     self.initial_paths = %w(