Register askar method does not work well if not imported on the first line #77
Description
We should tweak the registerAskar method to hold the askar object as part of another object. That way if the reference is updated, it's also updated in other places.
In addition we should make accessing the askar object a getter method, so that it resolves the reference each time.
Currently when you do not import askar on the first line (or above all logic that uses Askar) the reference will often be undefined (i.e. askar-shared is imported before askar-react-native or askar-nodejs)