📝 Add cover image

Author: Winston

README.md

@@ -2,6 +2,8 @@
 
 [![Known Vulnerabilities](https://snyk.io/test/github/winston0410/sparrow/badge.svg?targetFile=package.json)](https://snyk.io/test/github/winston0410/sparrow?targetFile=package.json) [![Maintainability](https://api.codeclimate.com/v1/badges/54626992beea73efcadf/maintainability)](https://codeclimate.com/github/winston0410/sparrow/maintainability) [![Codacy Badge](https://app.codacy.com/project/badge/Grade/4f5f78d7736d4ed7b8439c2096bdc38f)](https://www.codacy.com/manual/winston0410/sparrow?utm_source=github.com&utm_medium=referral&utm_content=winston0410/sparrow&utm_campaign=Badge_Grade) [![Test Coverage](https://api.codeclimate.com/v1/badges/54626992beea73efcadf/test_coverage)](https://codeclimate.com/github/winston0410/sparrow/test_coverage)
 
+![Cover image for PostCSS Sparrow](./cover.jpg)
+
 A PostCSS plugin that helps you **search CSS declarations** by **selectors**. Avoid the hassle of reinventing the wheel and filter selectors you want again when you create a new PostCSS plugin.