Improve formatting

Author: Grégoire Paris

core/jwt.md

@@ -80,7 +80,7 @@ And the "Authorize" button will automatically appear in Swagger UI.
 
 ### Adding a New API Key
 
-All you have to do is configure the API key in the value field.
+All you have to do is configure the API key in the `value` field.
 By default [only the authorization header mode is enabled](https://github.com/lexik/LexikJWTAuthenticationBundle/blob/master/Resources/doc/index.md#2-use-the-token) in [LexikJWTAuthenticationBundle](https://github.com/lexik/LexikJWTAuthenticationBundle).
 You must set the [JWT token](https://github.com/lexik/LexikJWTAuthenticationBundle/blob/master/Resources/doc/index.md#1-obtain-the-token) as below and click on the "Authorize" button.