Add "no-debugger" eslint rule

Author: GuillaumeGomez

src/librustdoc/html/static/.eslintrc.js

@@ -64,5 +64,6 @@ module.exports = {
         ],
         "eqeqeq": "error",
         "no-const-assign": "error",
+        "no-debugger": "error",
     }
 };