Auto merge of #91356 - GuillaumeGomez:improve-rustdoc-layout, r=jsha

Improve rustdoc layout

This is an overtake of #89385 originally written by `@cynecx.`

I kept the original commit and simply added the missing fixes into a new one. You can test it online [here](https://rustdoc.crud.net/imperio/improve-rustdoc-layout/std/index.html).

r? `@jsha`

src/librustdoc/html/markdown.rs

@@ -1447,7 +1447,7 @@ fn init_id_map() -> FxHashMap<String, usize> {
     map.insert("theme-choices".to_owned(), 1);
     map.insert("settings-menu".to_owned(), 1);
     map.insert("help-button".to_owned(), 1);
-    map.insert("main".to_owned(), 1);
+    map.insert("main-content".to_owned(), 1);
     map.insert("search".to_owned(), 1);
     map.insert("crate-search".to_owned(), 1);
     map.insert("render-detail".to_owned(), 1);

src/librustdoc/html/markdown/tests.rs

@@ -12,7 +12,7 @@ fn test_unique_id() {
         "examples",
         "method.into_iter",
         "foo",
-        "main",
+        "main-content",
         "search",
         "methods",
         "examples",
@@ -28,7 +28,7 @@ fn test_unique_id() {
         "examples-2",
         "method.into_iter-1",
         "foo-1",
-        "main-1",
+        "main-content-1",
         "search-1",
         "methods",
         "examples-3",
@@ -219,8 +219,8 @@ fn test_header_ids_multiple_blocks() {
     );
     t(
         &mut map,
-        "# Main",
-        "<h2 id=\"main-1\" class=\"section-header\"><a href=\"#main-1\">Main</a></h2>",
+        "# Search",
+        "<h2 id=\"search-1\" class=\"section-header\"><a href=\"#search-1\">Search</a></h2>",
     );
     t(
         &mut map,

src/librustdoc/html/static/css/noscript.css

@@ -4,7 +4,7 @@ of content is hidden by default (depending on the settings too), we have to over
 rules.
 */
 
-#main .attributes {
+#main-content .attributes {
 	/* Since there is no toggle (the "[-]") when JS is disabled, no need for this margin either. */
 	margin-left: 0 !important;
 }