Docs: Dogfood the "Tested with QUnit" badge

Author: Krinkle

CONTRIBUTING.md

@@ -9,7 +9,7 @@ anything should be added or clarified, definitely let us know.
 If this is your first time contributing to open-source software, you might want
 to take a look at the [GitHub Guides](https://guides.github.com/).
 
-If you get stuck or need help, you can always [chat with us](https://gitter.im/qunitjs/qunit).
+If you get stuck or need help, you can always [chat with us](https://app.element.io/#/room/#qunitjs_qunit:gitter.im).
 
 ## Where to begin
 

README.md

@@ -4,7 +4,7 @@
 
 [![Continuous integration](https://github.com/qunitjs/qunit/actions/workflows/CI.yaml/badge.svg)](https://github.com/qunitjs/qunit/actions/workflows/CI.yaml)
 [![Test coverage](https://coveralls.io/repos/qunitjs/qunit/badge.svg)](https://coveralls.io/github/qunitjs/qunit)
-[![Chat on Matrix](https://badges.gitter.im/Join%20Chat.svg)](https://app.element.io/#/room/#qunitjs_qunit:gitter.im)
+[![Tested with QUnit](https://qunitjs.com/testedwith.svg)](https://qunitjs.com/badge/)
 [![npm](https://img.shields.io/npm/v/qunit.svg?style=flat)](https://www.npmjs.com/package/qunit)
 [![Reproducible build status](https://img.shields.io/badge/Reproducible_Builds-ok-success?labelColor=1e5b96)](https://github.com/qunitjs/qunit/actions/workflows/reproducible.yaml)
 [![OpenSSF Best Practices](https://www.bestpractices.dev/projects/5751/badge)](https://www.bestpractices.dev/projects/5751)

docs/index.md

@@ -86,7 +86,7 @@ These are the official [release channels](intro.md#download) for QUnit:
 
 ## Join the Community
 
-<p class="lead lead--center" markdown="1">Join us on [Mastodon](https://fosstodon.org/@qunit), [Twitter](https://twitter.com/qunitjs), or [Matrix chat](https://gitter.im/qunitjs/qunit).</p>
+<p class="lead lead--center" markdown="1">Join us on [Mastodon](https://fosstodon.org/@qunit), [Twitter](https://twitter.com/qunitjs), or [Matrix chat](https://app.element.io/#/room/#qunitjs_qunit:gitter.im).</p>
 
 To contribute:
 

docs/upgrade-guide-2.x.md

@@ -216,7 +216,7 @@ QUnit.assert.mod2 = function (value, expected, message) {
 
 ### Removed `QUnit.init` without replacement
 
-This method used to reinitialize the test runner. It should never have been exposed as a public method and is now gone, without replacement. If you've built an integration or runner framework that requires the use of `QUnit.init`, reach out in our [Chat room](https://gitter.im/qunitjs/qunit), or contact us in the [issue tracker](https://github.com/qunitjs/qunit/issues) to help find a replacement.
+This method used to reinitialize the test runner. It should never have been exposed as a public method and is now gone, without replacement. If you've built an integration or runner framework that requires the use of `QUnit.init`, reach out in our [Chat room](https://app.element.io/#/room/#qunitjs_qunit:gitter.im), or contact us in the [issue tracker](https://github.com/qunitjs/qunit/issues) to help find a replacement.
 
 ### Removed `QUnit.reset`