[SSSD] [sssd PR#965][opened] certmap: mention special regex characters in man page

[sumit-bose]

   URL: https://github.com/SSSD/sssd/pull/965
Author: sumit-bose
 Title: #965: certmap: mention special regex characters in man page
Action: opened

PR body:
"""
Since some of the matching rules use regular expressions some characters
must be escaped so that they can be used a ordinary characters in the
rules.

Related to https://pagure.io/SSSD/sssd/issue/4127
"""

To pull the PR as Git branch:
git remote add ghsssd https://github.com/SSSD/sssd
git fetch ghsssd pull/965/head:pr965
git checkout pr965