style(readme): fix usage

Author: azu

README.md

@@ -43,12 +43,12 @@ Install with [npm](https://www.npmjs.com/):
 
 Via `.textlintrc`(Recommended)
 
-```json
+```js
 {
     "rules": {
         "eslint": {
           // Required: path to .eslintrc file
-          configFile: "path/to/.eslintrc"
+          "configFile": "path/to/.eslintrc"
         }
     }
 }
@@ -73,9 +73,9 @@ textlint --rule eslint README.md
     "rules": {
         "eslint": {
             // Required: path to .eslintrc file
-            configFile: "path/to/.eslintrc",
+            "configFile": "path/to/.eslintrc",
             // recognize lang of CodeBlock
-            langs: ["js", "javascript", "node", "jsx"]
+            "langs": ["js", "javascript", "node", "jsx"]
         }
     }
 }

src/textlint-rule-eslint.js

@@ -4,13 +4,13 @@ const CLIEngine = require("eslint").CLIEngine;
 const path = require("path");
 const defaultOptions = {
     // path to .eslintrc file
-    configFile: null,
+    "configFile": null,
     // recognize lang of CodeBlock
-    langs: ["js", "javascript", "node", "jsx"]
+    "langs": ["js", "javascript", "node", "jsx"]
 };
-module.exports = function (context, options) {
+module.exports = function(context, options) {
     const {Syntax, RuleError, report, getSource} = context;
-    if(!options.configFile) {
+    if (!options.configFile) {
         throw new Error(`Require options: { "configFile": "path/to/.eslintrc" }`);
     }
     const availableLang = options.langs || defaultOptions.langs;