textproc/py-rstfmt: Add new port
rstfmt is a tool for automatically formatting reStructuredText files in
a consistent way.
Like Black and gofmt, the motivation is to provide a format that is
reasonable and minimally configurable to prevent teams from wasting time
on style discussions (or individuals on manually doing formatting, for
that matter).
Currently, rstfmt is in a very early stage of development. Not all reST
constructs are covered and the interface or formatting may change at any
time without warning.