contrib: add editmerge version for powershell
This just adds a translation of existing contrib/editmerge to powershell.
It allows users on Windows to iteratively resolve conflicts in their
editor of choice.
# no-check-commit
Mercurial's documentation is kept in reStructuredText format, which is
a simple plain text format that's easy to read and edit:
http://docutils.sourceforge.net/rst.html
It's also convertible to a variety of other formats including standard
UNIX man page format and HTML. You'll need to install Docutils:
http://docutils.sourceforge.net/
Use the Makefile in this directory to generate the man and HTML pages.