Preflight success statusCode should be configurable

[Sharaal]

Hi,

we have currently problems in the communication with some Smart TVs. They crashs if getting a 204 status code for the preflight request and want to have a 200 status code.
Default value if not configured should be 204 for compatibility.

[Sharaal]

Would be also solved by always response the status code 200 like its mentioned in the already existing pull request: #66

[troygoode]

fixed and published as 2.8.0, but requires you to set the option optionsSuccessCode: 200

[hongbo-miao]

Just searched and found here, the current field name is optionsSuccessStatus.
Posted here in case it help future people.