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/components/context/DarkTheme.tsx

@@ -8,13 +8,13 @@
 import React from 'react';
 
 type ContextType = {
-    darkTheme: boolean
-    setDarkTheme: React.Dispatch<React.SetStateAction<boolean>>
+    darkTheme: boolean;
+    setDarkTheme: React.Dispatch<React.SetStateAction<boolean>>;
 };
 
 const DarkTheme = React.createContext<ContextType>({
     darkTheme: true,
-    setDarkTheme: ():void => {},
+    setDarkTheme: (): void => {},
 });
 
 export default DarkTheme;