docs: update badges

README.md

@@ -4,8 +4,7 @@
 
 [![Release](https://img.shields.io/github/release/Requarks/wiki.svg?style=flat&maxAge=3600)](https://github.com/Requarks/wiki/releases)
 [![License](https://img.shields.io/badge/license-AGPLv3-blue.svg?style=flat)](https://github.com/requarks/wiki/blob/master/LICENSE)
-[![Backers on Open Collective](https://opencollective.com/wikijs/backers/badge.svg)](#backers)
-[![Sponsors on Open Collective](https://opencollective.com/wikijs/sponsors/badge.svg)](#sponsors)
+[![Backers on Open Collective](https://opencollective.com/wikijs/all/badge.svg)](https://opencollective.com/wikijs)
 [![Downloads](https://img.shields.io/github/downloads/Requarks/wiki/total.svg?style=flat)](https://www.npmjs.com/package/wiki.js)
 [![Docker Pulls](https://img.shields.io/docker/pulls/requarks/wiki.svg)](https://hub.docker.com/r/requarks/wiki/)  
 [![Build status](https://dev.azure.com/requarks/wiki/_apis/build/status/build)](https://dev.azure.com/requarks/wiki/_build/latest?definitionId=9)
@@ -13,7 +12,7 @@
 [![Maintainability Rating](https://sonarcloud.io/api/project_badges/measure?project=wiki&metric=sqale_rating)](https://sonarcloud.io/dashboard?id=wiki)
 [![Security Rating](https://sonarcloud.io/api/project_badges/measure?project=wiki&metric=security_rating)](https://sonarcloud.io/dashboard?id=wiki)
 [![Standard - JavaScript Style Guide](https://img.shields.io/badge/code%20style-standard-brightgreen.svg?style=flat)](http://standardjs.com/)  
-[![Chat on Gitter](https://img.shields.io/badge/chat-on_gitter-CC2B5E.svg?style=flat&logo=image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAcAAAAOCAMAAADUg/YpAAAABlBMVEUAAAD///%2Bl2Z/dAAAAAXRSTlMAQObYZgAAABVJREFUeAFjwAUYYTQByAAh0WicAAAFnwAYeB5bLwAAAABJRU5ErkJggg==)](https://gitter.im/Requarks/wiki)
+[![Chat on Slack](https://img.shields.io/badge/slack-requarks-CC2B5E.svg?style=flat&logo=slack)](https://join.slack.com/t/requarks/shared_invite/enQtNjQ2MjQ1NTY2Mjg5LTBjOTc3YzBjM2M2ODc3ZDM2ZjdlNjBkZTdmZjM4M2QwM2VjZTk0ZjZkY2M0YjdkYTYwZDUwNzBkODcxMjQxOWU)
 [![Twitter Follow](https://img.shields.io/badge/follow-%40requarks-blue.svg?style=flat&logo=twitter)](https://twitter.com/requarks)
 [![Subscribe to Newsletter](https://img.shields.io/badge/newsletter-subscribe-yellow.svg?style=flat&logo=mailchimp)](https://wiki.js.org/newsletter)