Enforce no trailing spaces with eslint

Author: GuillaumeGomez

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

@@ -25,6 +25,7 @@ module.exports = {
             "error",
             "unix"
         ],
+        "no-trailing-spaces": "error",
         "no-var": ["error"],
         "prefer-const": ["error"],
         "prefer-arrow-callback": ["error"],