updating and adding other links to slack and Twitter

Author: kalwalt

Readme.md

@@ -1,3 +1,4 @@
 # WebARkit.github.io
 
-Official WebARkit org website 
+Official WebARkit org website.
+Join us at the [slack channel.](https://join.slack.com/t/webarkit/shared_invite/zt-eupovakz-7e2spEifwn~rOHC0vpaWhw) or follw us on Twitter: [@WebarkitO](https://twitter.com/WebarkitO) 

_posts/2020-05-06-welcome-to-webarkit.markdown

@@ -23,5 +23,5 @@ Unfortunately as regards **WebARStudio**, some improvements have been made but n
 An interesting mention should be made for the CSS renderer developed by Daniel Fernandes based on the Threejs CSS3D renderer, many interesting possibilities open up with this project !!
 
 Finally, the icing on the cake is the incredible work done by hiukim [mind-ar-js](https://github.com/webarkit/mind-ar-js), he has in fact translated the Artoolkit code concerning the NFT with gpu.js, creating a version completely made for the GPU!! For sure this will be the future of augmented reality... Obviously the code needs to be improved and most likely the algorithm needs to be changed. But in the meantime: Very good hiukim! Great!
-If you are interested, follow us and subscribe to our web page or follow our Twitter profile [@WebarkitO](https://twitter.com/WebarkitO), and if you want to get in touch with us to participate and contribute to the project, let's meet in our [slack channel](https://join.slack.com/t/webarkit/shared_invite/zt-ecq9duuo-hNBNqXVfp6DRDU_5QwI~XA), we are open for collaborations.
+If you are interested, follow us and subscribe to our web page or follow our Twitter profile [@WebarkitO](https://twitter.com/WebarkitO), and if you want to get in touch with us to participate and contribute to the project, let's meet in our [slack channel](https://join.slack.com/t/webarkit/shared_invite/zt-eupovakz-7e2spEifwn~rOHC0vpaWhw), we are open for collaborations.
 Stay tuned!