update remaining slack links (refs aframevr#4941) (aframevr#4962)

CONTRIBUTING.md

@@ -1,4 +1,4 @@
-[slack]: https://aframe.io/slack-invite/
+[slack]: https://aframevr.slack.com/join/shared_invite/zt-f6rne3ly-ekVaBU~Xu~fsZHXr56jacQ
 [stackoverflow]: http://stackoverflow.com/questions/tagged/aframe
 
 Interested in contributing? As an open source project, we'd appreciate any help

docs/introduction/faq.md

@@ -9,7 +9,7 @@ order: 14
 [ecs]: ./entity-component-system.md
 [github]: http://github.com/aframevr/aframe/
 [three]: http://threejs.org
-[slack]: https://aframe.io/slack-invite/
+[slack]: https://aframevr.slack.com/join/shared_invite/zt-f6rne3ly-ekVaBU~Xu~fsZHXr56jacQ
 [twitter]: https://twitter.com/aframevr/
 [stackoverflow]: http://stackoverflow.com/questions/tagged/aframe/
 

docs/introduction/index.md

@@ -159,7 +159,7 @@ as Google, Microsoft, Oculus, and Samsung have made contributions to A-Frame.
 ## Off You Go!
 
 [Discord]: https://supermedium.com/discord
-[slack]: https://aframe.io/slack-invite/
+[slack]: https://aframevr.slack.com/join/shared_invite/zt-f6rne3ly-ekVaBU~Xu~fsZHXr56jacQ
 
 If it's your first time here, here's a plan for success for getting into
 A-Frame:

examples/index.html

@@ -123,7 +123,7 @@ <h1>A-Frame Examples</h1>
       <ul id="resources" class="resources">
         <li><a href="https://aframe.io">aframe.io</a></li>
         <li><a href="https://github.com/aframevr">GitHub</a></li>
-        <li><a href="https://aframe.io/slack-invite/">Slack</a></li>
+        <li><a href="https://aframevr.slack.com/join/shared_invite/zt-f6rne3ly-ekVaBU~Xu~fsZHXr56jacQ">Slack</a></li>
         <li><a href="https://twitter.com/aframevr">Twitter</a></li>
         <li><a href="https://webvr.directory">Showcase Directory</a></li>
       </ul>