add doc(alias("AsciiChar")) to core::ascii::Char

Added it to the reexported, which is intended
rustdoc behavior, but is apparently untested,
so I also added a test for it.

library/core/src/ascii.rs

@@ -15,6 +15,7 @@
 use crate::num::NonZero;
 
 mod ascii_char;
+#[doc(alias("AsciiChar"))]
 #[unstable(feature = "ascii_char", issue = "110998")]
 pub use ascii_char::AsciiChar as Char;
 

tests/rustdoc-js-std/doc-alias-use.js

@@ -0,0 +1,12 @@
+// AsciiChar has a doc alias on its reexport and we
+// want to make sure that actually works correctly,
+// since apperently there are no other tests for this.
+
+const EXPECTED = [
+    {
+        'query': 'AsciiChar',
+        'others': [
+            { 'path': 'core::ascii', 'name': 'Char' },
+        ],
+    },
+];