New Release: 0.3.1

[D-o-d-o-x]

There were two issues with our pipeline identified during the 0.3.0 release (#97 ):

• docs were not successfully updated due to a permission issue.
• compiled packages were not pushed to PyPI due to a roblem with the workflow (#103)

These issues were now fixed.

Contained additions:

• #100: Added smoothness metrics to BoxPushing and new env variants for TableTennis and HopperJump.

We will wait for these to be merged into master before the release is issued.