Exposing the entries of a custom `map` instead of its methods

Since 4e76d8820401fbc3a2d128e5fcc4674519fe9850 any map type implementing methods will cause those methods to be exposed to JS, but not any of the map entries, to avoid ambiguity.

Now I'm in a scenario where I need the exact opposite behavior: all the map entries should be exposed as properties and none of the methods.

This could be solved with a customizable ToValue: #426

Would you prefer solving this issue via #426 or would you accept a PR with an alternative solution for this case specifically?

For instance, we could use "marker" interfaces:

type ExportEntries interface {
  GojaExportEntries()
}

type Foo map[string]string

// GojaExportEntries is used as a marker for goja to export the map entries instead of its methods.
func (_ Foo) GojaExportEntries() {}

// Without the above, the map would always be exported as an object with this method only.
func (f Foo) SomeMethod() {}