Update basicwebsite.wiki

[pwbs]

Inform explicitly that Eliom_registration.Html_text.create does both the creation and the registration of the service.

However I'm not sure it's how it should be done...

[vasilisp]

That comment doesn't harm, so merging. But I don't know where (else) to put this clarification either. It is already in the relevant signatures, but the documentation has so many entry points that points like this are easy to be missed.

[pwbs]

Thanks.