bugfix(docs): inside nodejs markdown badly formatted

- 'Inside Node.js' had a missing table header on the attributes table, causing the table to be rendered incorrectly

Author: dazgreer

doc/install.md

@@ -100,7 +100,7 @@ console.log(htmlOutput)
 ```
 
 You can pass optional `options` as an object to the `mjml2html` function:
-
+option                  | accepts      | description                                                                                                                                               | default value
 | -------------------- | ------- | ------------------------------------------------------------------------------------------------------------------------------------------------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
 | fonts                | object  | Default fonts imported in the HTML rendered by MJML                                                                                                    | See in [index.js](https://github.com/mjmlio/mjml/blob/master/packages/mjml-core/src/index.js#L100-L108)                                                                                                                                                                                                                                                                           |
 | keepComments         | boolean | Option to keep comments in the HTML output                                                                                                             | `true`                                                                                                                                                                                                                                                                                                                                                                            |