Support @http options functions

Describe the issue Today, one cannot create a function to handle HTTP options preflight requests; those instead wind up falling back to get / to be handled for all endpoints.

That’s probably fine for many cases, but likely anyone being mindful of how they handle CORS preflight requests will want to set up an actual proper options endpoint.

It’d probably look like this:

@http
get     /foo # src/http/get-foo
put     /foo # src/http/put-foo
options /foo # [new!] src/http/options-foo

[krimple]

ok, will do.

[AustinGil]

Yeah. I’ve made a couple small edits, but I’d like to get a better grip on things and then start contributing more. In any case, hopefully some of the discussion here will help folks that DuckDuckGo it.