Add miri to the rustc docs.rs page

This adds miri to https://doc.rust-lang.org/nightly/nightly-rustc/

Signed-off-by: InfRandomness <infrandomness@gmail.com>

src/bootstrap/builder.rs

@@ -694,6 +694,7 @@ impl<'a> Builder<'a> {
                 doc::RustcBook,
                 doc::CargoBook,
                 doc::Clippy,
+                doc::Miri,
                 doc::EmbeddedBook,
                 doc::EditionGuide,
             ),

src/bootstrap/doc.rs

@@ -737,6 +737,7 @@ tool_doc!(
     ["rustfmt-nightly", "rustfmt-config_proc_macro"],
 );
 tool_doc!(Clippy, "clippy", "src/tools/clippy", ["clippy_utils"]);
+tool_doc!(Miri, "miri", "src/tools/miri", ["miri"]);
 
 #[derive(Ord, PartialOrd, Debug, Copy, Clone, Hash, PartialEq, Eq)]
 pub struct ErrorIndex {