New project: echoplexus #100

* logo from https://github.com/qq99/echoplexus/blob/master/assets/echoplexus-logo.png resized to 130×130 and centered in 160×160
* license from https://github.com/qq99/echoplexus/blob/master/LICENSE
* introduction from https://github.com/qq99/echoplexus/blob/master/README.md (excerpt)

Echoplex is too good to wait for someone to do this in some months (even not sure), so here’s it! 
»group communication« is a bit too long. Remember it will be shown on hover. It’s not only »chat« for sure. Let’s just go with »collaboration« for now. We can still change it when we see it’s not a good fit.