Merge '11-rework-landing-page' into 'main'

Reworks the landing page of the application by adding a new hero-banner with a searchbar for a quick regesta search. Additionally implements a new formatting helper function that finds search terms within regesta summaries, highlights their occurence and calculates a substring of the summary that displays the text around the occurence.

Also reworks the feature previews on the landing-page by creating card-based, clickable preview with a hover effect.

Closes #11 (closed)