Added prettier config with single quotes.

Not yet enforcing prettier on the code base.
This is for future changes.
And if we will chose to prettify the entire code base, I prefer single quotes since we have been using them in all across the documentation.

Author: dfahlander

.prettierrc

@@ -0,0 +1,5 @@
+{
+  "trailingComma": "es5",
+  "tabWidth": 2,
+  "singleQuote": true
+}