Bazel docs: Fix Edit button

The new doc website has a new URL structure. This change adapts the page extraction code.
It also restores the CSS for the edit button which got deleted during refactoring.

Fix #3272

RELNOTES: None
PiperOrigin-RevId: 160279009
diff --git a/site/css/main.scss b/site/css/main.scss
index 0ee13b8..402b94f 100644
--- a/site/css/main.scss
+++ b/site/css/main.scss
@@ -5,6 +5,7 @@
 @import "footer.scss";
 @import "navbar.scss";
 @import "sidebar.scss";
+@import "docs.scss";
 @import "be.scss";
 
 @import "syntax.scss";