[js-api] "Creating a host function" requires a functype parameter

[rossberg]

The algorithm to create a host function uses the function's type:

• in step 1.1 implicitly as "the signature",
• in step 1.6 as |functype|.

However, that type is not actually provided. The algorithm needs to take |functype| as a parameter.

[littledan]

This is actually fixed only in 24e291c cc @Ms2ger

[littledan]

That patch landed too, so closing.