Support for "defaultLoginOptions" on "init" method in keycloak.js

Method "login" of keycloak.js supports few options to customize login flow. For example things like "scope", "prompt" or "max_age" .

The method "init" doesn't support those, so if you have an application with "required" login, it is not easily possible to add custom prompt or scope. Will be good if method "init" can accept something like "defaultLoginOptions", which will allow to add things like "prompt" or "scope"