Rollup merge of #142472 - GuillaumeGomez:doc-attribute-attribute, r=fmease

Add new `doc(attribute = "...")` attribute

Fixes rust-lang/rust#141123.

The implementation and purpose of this new `#[doc(attribute = "...")]` attribute is very close to `#[doc(keyword = "...")]`. Which means that luckily for us, most of the code needed was already in place and `@Noratrieb` nicely wrote a first draft that helped me implement this new attribute very fast.

Now with all this said, there is one thing I didn't do yet: adding a `rustdoc-js-std` test. I added GUI tests with search results for attributes so should be fine but I still plan on adding one for it once documentation for builtin attributes will be written into the core/std libs.

You can test it [here](https://rustdoc.crud.net/imperio/doc-attribute-attribute/foo/index.html).

cc `@Noratrieb` `@Veykril`

1 files changed, 1 insertions, 0 deletions

diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 89b07dba5c8..77260d07c99 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -541,6 +541,7 @@ symbols! {
         att_syntax,
         attr,
         attr_literals,
+        attribute,
         attributes,
         audit_that,
         augmented_assignments,