Make compatible with excel addin

[marijnvanderhorst]

Is your feature request related to a problem? Please describe.
It seems that this package cannot be used directly in the marketredesign/pricecypher_excel_addin application, even though that is technically just a SPA using Vue 2. (this is what Kadir concluded so we should check first if this is actually the case)

Describe the solution you'd like
Figure out why (if at all) it's not working in the excel addin and fix it.
NB: make sure to include the onAuthenticatedCallback functionality that was added in the excel addin (src/auth/index.js)

Describe alternatives you've considered
Excel addin currently just has a copy of these files, which does work technically.

Additional context
n/a