Update CORS for Oxford Dictionary API (#811)

https://forum.oxforddictionaries.com/api/discussion/18/error-message-no-access-control-allow-origin-or-i-can-t-get-my-client-side-request-to-work
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Unfortunately, we are unable to support client-side application requests (this includes JavaScript, JScript, VBScript, Java applets, ActionScript, etc.).

> This is because our API does not currently support CORS requests due to the potential implications for the security of our server. 
> Instead, we suggest you to make the query reach your server side application, and then send the API request from the server rather than from the client.

README.md

@@ -264,7 +264,7 @@ API | Description | Auth | HTTPS | CORS |
 API | Description | Auth | HTTPS | CORS |
 |---|---|---|---|---|
 | [Merriam-Webster](https://dictionaryapi.com/) | Dictionary and Thesaurus Data | `apiKey` | Yes | Unknown |
-| [Oxford](https://developer.oxforddictionaries.com/) | Dictionary Data | `apiKey` | Yes | Unknown |
+| [Oxford](https://developer.oxforddictionaries.com/) | Dictionary Data | `apiKey` | Yes | No |
 | [Wordnik](http://developer.wordnik.com) | Dictionary Data | `apiKey` | No | Unknown |
 | [Words](https://www.wordsapi.com/) | Definitions and synonyms for more than 150,000 words | `apiKey` | Yes | Unknown |