Provide link to MediaWiki platform specific page
Provide link to MediaWiki platform specific page

Provide a link to the MediaWiki page on git-review installation, which
provides details for a range of platforms, including Windows and OS
X/macOS.

Change-Id: If030fa7614a7cea33c2a55605a6f0d68751173ea
Story: #2000481

openstack-infra/git-review