feat: design on authorization page (startinblox/applications/sib-app#224)

I'm not completely satisfied with how styles are managed here. I had to duplicate code since CSS is majorly managed on front-end and does not use classes but custom component names. This is probably an improvement in the future.

Edit: it is possible to render this page on front-end using the ability to ask user's permission in a popup generated by solid-auth-client.