message: Add Percy badge
diff: @@ -14,6 +14,7 @@ Accessible, customizable, delightful date & time pickers for [@material-ui/core]
  [![Bundle Size](https://badgen.net/bundlephobia/minzip/@material-ui/pickers)](https://bundlephobia.com/result?p=@material-ui/pickers@latest)
  [![CircleCI](https://circleci.com/gh/mui-org/material-ui-pickers.svg?style=svg)](https://circleci.com/gh/mui-org/material-ui-pickers)
  [![Cypress.io tests](https://img.shields.io/badge/cypress.io-tests-green.svg?style=flat-square)](https://dashboard.cypress.io/#/projects/qow28y/runs)
  +[![This project is using Percy.io for visual regression testing.](https://percy.io/static/images/percy-badge.svg)](https://percy.io/mui-org/material-ui-pickers)
  [![code style: prettier](https://img.shields.io/badge/code_style-prettier-ff69b4.svg?style=flat-square)](https://github.com/prettier/prettier)
  </div>
  