[postfixadmin/postfixadmin] b1b432: add commit activity badge

[David G. <no...@gi...>]

  Branch: refs/heads/master
  Home:   https://github.com/postfixadmin/postfixadmin
  Commit: b1b4324a5b725549a0b2a17e6986f1fc4d7325f2
      https://github.com/postfixadmin/postfixadmin/commit/b1b4324a5b725549a0b2a17e6986f1fc4d7325f2
  Author: David Goodwin <da...@co...>
  Date:   2022-08-02 (Tue, 02 Aug 2022)

  Changed paths:
    M README.md

  Log Message:
  -----------
  add commit activity badge

lifted from shields.io / https://github.com/badges/shields/blob/master/README.md