Added Options Method

[RyanBrunoUSDC]

Because Ambiorix is unopinionated it should give users the ability to handle the OPTIONS http method. With this in place you can handle CORS pre-flight requests like:

app$options("/route", function(req, res) {
    res$send("", headers = list(
                        `Access-Control-Allow-Origin` = "*",
                        `Access-Control-Allow-Methods` = "*",
                        `Access-Control-Allow-Headers` = "*"))
})

app$all is left alone to not break existing code. But this is up to the maintainers.

[JohnCoene]

I had overlooked this thank you.

{ambiorix} takes inspiration from express.js which allows adding headers on the response object (res) with a method, e.g.: addHeader("Access-Control-Allow-Origin", "*")

[JohnCoene]

Sorry, misread your PR, apologies.