[GSoC-Week7] Release v0.5.0

[Sid-Bhatia-0]

cc @findmyway @jonathan-laurent

Last week:

I created and submitted the recording for my talk. https://pretalx.com/juliacon2021/talk/DX7DCQ/

Towards the end, I also reimplemented some more environments as per the new design. #164 #165 #166

This week:

It would be great if I can release v0.5.0 by the end of this week.
As pointed out by @findmyway in last week's discussion (#163 (comment)), it would also require updating related experiments in RLZoo.