Frontend - edit functionality for cards

[wisskirchenj]

Provide a new CardEdit Vue component to edit existing Card - documents.

• component is conditionally rendered inside CardsPage.vue
• component is accessed with the EditMdiButton in CardDetails.vue component and replaces the latter upon activation inside the CardsPage
• component consists of all data attributes relevant for the current type of (Flash-)card (except id and createdAt), which have to be made editable. I.e. the attributes
  • title,
  • question,
  • tags,
  • answer *,
  • options *,
  • correctOption * and
  • correctOptions ( type-dependent)
• the CardType (currently Question&Answer, Single- and Multiple-Choice-Quiz) can not be changed (for simplicity reasons - to not overcomplicate layouting)
• layouting of the data fields should generally (in sequence) follow the one in the existing CardDetail component.
• To achieve a mantainable and reusable code and support all Card subtypes, the CardEdit component should probably be structured further into subcomponents - alternatively we can provide different components for each subtype.
• a wiremock design is preferrable, as UI-design (e.g. for adding, removing tags or options, defining correctOptions) is not trivial.