Add @sivkoff to the contributors table

Author: vitalyso

.all-contributorsrc

@@ -558,6 +558,15 @@
       "contributions": [
         "doc"
       ]
+    },
+    {
+      "login": "sivkoff",
+      "name": "Vitaly Sivkov",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/2699953?v=4",
+      "profile": "http://sivkoff.com",
+      "contributions": [
+        "code"
+      ]
     }
   ]
 }

README.md

@@ -15,7 +15,7 @@
 [![version][version-badge]][package] [![downloads][downloads-badge]][npmtrends]
 [![MIT License][license-badge]][license]
 
-[![All Contributors](https://img.shields.io/badge/all_contributors-57-orange.svg?style=flat-square)](#contributors)
+[![All Contributors](https://img.shields.io/badge/all_contributors-58-orange.svg?style=flat-square)](#contributors)
 [![PRs Welcome][prs-badge]][prs] [![Code of Conduct][coc-badge]][coc]
 [![Join the community on Spectrum][spectrum-badge]][spectrum]
 
@@ -1305,6 +1305,7 @@ Thanks goes to these people ([emoji key][emojis]):
 | [<img src="https://avatars3.githubusercontent.com/u/881986?v=4" width="100px;"/><br /><sub><b>dadamssg</b></sub>](https://github.com/dadamssg)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=dadamssg "Documentation") | [<img src="https://avatars0.githubusercontent.com/u/8734097?v=4" width="100px;"/><br /><sub><b>Yazan Aabed</b></sub>](https://www.yaabed.com/)<br />[📝](#blog-YazanAabeed "Blogposts") | [<img src="https://avatars0.githubusercontent.com/u/556258?v=4" width="100px;"/><br /><sub><b>Tim</b></sub>](https://github.com/timbonicus)<br />[🐛](https://github.com/kentcdodds/react-testing-library/issues?q=author%3Atimbonicus "Bug reports") [💻](https://github.com/kentcdodds/react-testing-library/commits?author=timbonicus "Code") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=timbonicus "Documentation") [⚠️](https://github.com/kentcdodds/react-testing-library/commits?author=timbonicus "Tests") | [<img src="https://avatars3.githubusercontent.com/u/6682655?v=4" width="100px;"/><br /><sub><b>Divyanshu Maithani</b></sub>](http://divyanshu.xyz)<br />[✅](#tutorial-divyanshu013 "Tutorials") [📹](#video-divyanshu013 "Videos") | [<img src="https://avatars2.githubusercontent.com/u/9116042?v=4" width="100px;"/><br /><sub><b>Deepak Grover</b></sub>](https://www.linkedin.com/in/metagrover)<br />[✅](#tutorial-metagrover "Tutorials") [📹](#video-metagrover "Videos") | [<img src="https://avatars0.githubusercontent.com/u/16276358?v=4" width="100px;"/><br /><sub><b>Eyal Cohen</b></sub>](https://github.com/eyalcohen4)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=eyalcohen4 "Documentation") | [<img src="https://avatars3.githubusercontent.com/u/7452681?v=4" width="100px;"/><br /><sub><b>Peter Makowski</b></sub>](https://github.com/petermakowski)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=petermakowski "Documentation") |
 | [<img src="https://avatars2.githubusercontent.com/u/20361668?v=4" width="100px;"/><br /><sub><b>Michiel Nuyts</b></sub>](https://github.com/Michielnuyts)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=Michielnuyts "Documentation") | [<img src="https://avatars0.githubusercontent.com/u/1195863?v=4" width="100px;"/><br /><sub><b>Joe Ng'ethe</b></sub>](https://github.com/joeynimu)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=joeynimu "Code") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=joeynimu "Documentation") | [<img src="https://avatars3.githubusercontent.com/u/19998290?v=4" width="100px;"/><br /><sub><b>Kate</b></sub>](https://github.com/Enikol)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=Enikol "Documentation") | [<img src="https://avatars1.githubusercontent.com/u/11980217?v=4" width="100px;"/><br /><sub><b>Sean</b></sub>](http://www.seanrparker.com)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=SeanRParker "Documentation") | [<img src="https://avatars2.githubusercontent.com/u/17031?v=4" width="100px;"/><br /><sub><b>James Long</b></sub>](http://jlongster.com)<br />[🤔](#ideas-jlongster "Ideas, Planning, & Feedback") [📦](#platform-jlongster "Packaging/porting to new platform") | [<img src="https://avatars1.githubusercontent.com/u/10118777?v=4" width="100px;"/><br /><sub><b>Herb Hagely</b></sub>](https://github.com/hhagely)<br />[💡](#example-hhagely "Examples") | [<img src="https://avatars2.githubusercontent.com/u/5779538?v=4" width="100px;"/><br /><sub><b>Alex Wendte</b></sub>](http://www.wendtedesigns.com/)<br />[💡](#example-themostcolm "Examples") |
 | [<img src="https://avatars0.githubusercontent.com/u/6998954?v=4" width="100px;"/><br /><sub><b>Monica Powell</b></sub>](http://www.aboutmonica.com)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=M0nica "Documentation") |
+| [<img src="https://avatars1.githubusercontent.com/u/2699953?v=4" width="100px;"/><br /><sub><b>Vitaly Sivkov</b></sub>](http://sivkoff.com)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=sivkoff "Code") |
 
 <!-- ALL-CONTRIBUTORS-LIST:END -->