docs: update README to include types badge, feature entry

Author: mrodrig

README.md

@@ -6,11 +6,11 @@
 [![NPM version](https://img.shields.io/npm/v/json-2-csv.svg)](https://www.npmjs.org/package/json-2-csv)
 [![Known Vulnerabilities](https://snyk.io/test/npm/json-2-csv/badge.svg)](https://snyk.io/test/npm/json-2-csv)
 [![Package Size](https://img.shields.io/bundlephobia/min/json-2-csv.svg)](https://www.npmjs.org/package/json-2-csv)
+[![Typings](https://shields-staging.herokuapp.com/npm/types/json-2-csv.svg?style=flat)](https://www.npmjs.org/package/json-2-csv)
 
 [![Build Status](https://travis-ci.org/mrodrig/json-2-csv.svg?branch=master)](https://travis-ci.org/mrodrig/json-2-csv)
 [![Maintainability](https://api.codeclimate.com/v1/badges/8c0cc3699d054fb77abe/maintainability)](https://codeclimate.com/github/mrodrig/json-2-csv/maintainability)
 [![Test Coverage](https://api.codeclimate.com/v1/badges/8c0cc3699d054fb77abe/test_coverage)](https://codeclimate.com/github/mrodrig/json-2-csv/test_coverage)
-[![Donate](https://img.shields.io/badge/Donate-PayPal-green.svg)](https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=rodrigues.mi%40husky.neu.edu&item_name=Open+Source+Software+Development+-+Node+Modules&currency_code=USD&source=url)
 
 This node module will convert an array of JSON documents to a CSV string.
 Column headings will be automatically generated based on the keys of the JSON documents. Nested documents will have a '.' appended between the keys.
@@ -203,3 +203,4 @@ Please find the updated list (relocated to the Wiki) here: [Frequently Asked Que
 	* *and*
 	* `json2csv test.json -o output.csv -W -k arrayOfStrings -o output.csv`
 * Empty field value option (as of 3.1.0)
+* TypeScript typings included (as of 3.4.0) - thanks to [@GabrielCastro](https://github.com/GabrielCastro)!