Add prettier config

This is the same config as WalletKit for consistency

Author: fredericboivin

.prettierrc

@@ -0,0 +1,8 @@
+{
+  "jsxSingleQuote": true,
+  "singleQuote": true,
+  "semi": true,
+  "trailingComma": "all",
+  "useTabs": false,
+  "tabWidth": 2
+}