Rollup merge of rust-lang#74325 - GuillaumeGomez:focus-source-file-sidebar, r=kinnison

Focus on the current file in the source file sidebar

Fixes rust-lang#73360.

r? @kinnison
cc @rust-lang/rustdoc

Author: Manishearth

src/librustdoc/html/static/source-script.js

@@ -140,4 +140,9 @@ function createSourceSidebar() {
     });
 
     main.insertBefore(sidebar, main.firstChild);
+    // Focus on the current file in the source files sidebar.
+    var selected_elem = sidebar.getElementsByClassName("selected")[0];
+    if (typeof selected_elem !== "undefined") {
+        selected_elem.focus();
+    }
 }