Support inner attributes inside bridge

Example:

    #[cxx::bridge]
    mod ffi {
        #![deny(missing_docs)]

        unsafe extern "C++" {
            include!("example/include/header.h");

            /// wow
            fn f();
        }
    }

    pub use self::ffi::*;
diff --git a/syntax/attrs.rs b/syntax/attrs.rs
index 4808f2e..0ced368 100644
--- a/syntax/attrs.rs
+++ b/syntax/attrs.rs
@@ -224,7 +224,19 @@
 impl ToTokens for OtherAttrs {
     fn to_tokens(&self, tokens: &mut TokenStream) {
         for attr in &self.0 {
-            attr.to_tokens(tokens);
+            let Attribute {
+                pound_token,
+                style,
+                bracket_token,
+                path,
+                tokens: attr_tokens,
+            } = attr;
+            pound_token.to_tokens(tokens);
+            let _ = style; // ignore; render outer and inner attrs both as outer
+            bracket_token.surround(tokens, |tokens| {
+                path.to_tokens(tokens);
+                attr_tokens.to_tokens(tokens);
+            });
         }
     }
 }