textproc/py-pscript: New port: Python to JavaScript compiler

PScript is a Python to JavaScript compiler, and is also the name
of the subset of Python that this compiler supports. It was developed
as a part of Flexx and is now represented by its own project.
Although it is still an important part of Flexx, it can also be
useful by itself.

WWW: https://pscript.readthedocs.io/
PR: 282453