Rollup merge of rust-lang#97990 - GuillaumeGomez:eslint-checks, r=Dylan-DPC

Add more eslint checks

List of newly added checks:

 * [no-lonely-if](https://eslint.org/docs/rules/no-lonely-if)
 * [no-mixed-operators](https://eslint.org/docs/rules/no-mixed-operators)
 * [no-multi-assign](https://eslint.org/docs/rules/no-multi-assign)
 * [no-return-assign](https://eslint.org/docs/rules/no-return-assign)
 * [no-script-url](https://eslint.org/docs/rules/no-script-url)

r? `@Dylan-DPC`

Author: matthiaskrgr

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

@@ -84,5 +84,10 @@ module.exports = {
         "no-implicit-globals": "error",
         "no-implied-eval": "error",
         "no-label-var": "error",
+        "no-lonely-if": "error",
+        "no-mixed-operators": "error",
+        "no-multi-assign": "error",
+        "no-return-assign": "error",
+        "no-script-url": "error",
     }
 };