ISCHWI-8705: Add about-page
This MR adds an about-page, and differentiates the content in the about- and the help-page. The about page is visible to all users, whereas the help-page only is visible to users with integrator access (or higher). See original MR: https://gitlab.esss.lu.se/ccce/dev/ccdb-ui-prototype/-/merge_requests/99