fix(v2): remove accessible anchors via keyboard

Author: lex111

packages/docusaurus-theme-classic/src/theme/Heading/index.js

@@ -17,8 +17,8 @@ const Heading = Tag => ({id, ...props}) => {
   }
   return (
     <Tag {...props}>
-      <a aria-hidden="true" className="anchor" id={id} />
-      <a aria-hidden="true" className="hash-link" href={`#${id}`}>
+      <a aria-hidden="true" tabIndex="-1" className="anchor" id={id} />
+      <a aria-hidden="true" tabIndex="-1" className="hash-link" href={`#${id}`}>
         #
       </a>
       {props.children}