[guide] Add an anchor for rule 13.7

Author: aifreedom

README.md

@@ -1701,6 +1701,7 @@ Other Style Guides
     const truthyCount = array.filter(Boolean).length;
     ```
 
+<a name="variables--linebreak"></a>
   - [13.7](#variables--linebreak) Avoid linebreaks before or after `=` in an assignment. If your assignment violates [`max-len`](https://eslint.org/docs/rules/max-len.html), surround the value in parens. eslint [`operator-linebreak`](https://eslint.org/docs/rules/operator-linebreak.html).
 
     > Why? Linebreaks surrounding `=` can obfuscate the value of an assignment.