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

.prettierrc

@@ -0,0 +1,7 @@
+{
+  "tabWidth": 4,
+  "singleQuote": true,
+  "printWidth": 100,
+  "semi": true,
+  "trailingComma": "all"
+}