JS API for exact function imports and exports.

[tlively]

Exact function imports are currently formulated as having the existing func kind, but now the functype that goes along with it includes exactness. If we don't change anything, the [imports()](https://webassembly.github.io/spec/js-api/index.html#dom-module-imports) method in the JS API will just report the exact function import as having kind "function" just like any other function import. Similarly there will be no way to distinguish exact and inexact exports.

Is it worth doing anything different here, or should we wait for a more general type reflection API to expose exactness in imports and exports?

My take is that the status quo is probably fine.