add prettier for auto formatting (#231)

* [Prettier] Add "prettier"

Makes the formatting of the code consistent.
By using the eslint-plugin-prettier formatting issues will be highlighted as a lint error.
These errors will be auto fixed by running "lint --fix" (which can be done automatically on file save)

* [Prettier] Add "prettier" - Fix formatting

src/util/useBackTo.ts

@@ -10,7 +10,7 @@ import { useLocation } from 'react-router-dom';
 
 export const BACK = '__BACK__';
 
-const useBackTo = (): { url?: string, back: boolean } => {
+const useBackTo = (): { url?: string; back: boolean } => {
     const location = useLocation<{ backLink?: string }>();
     const { defaultBackTo } = useNavBarContext();