[GRASS-git] [OSGeo/grass] 8a90b1: Issues are now on GitHub (#315)

[Vaclav Petras]

  Branch: refs/heads/master
  Home:   https://github.com/OSGeo/grass
  Commit: 8a90b1fc7982d996b96c92f8172dbbc3875fdccd
      https://github.com/OSGeo/grass/commit/8a90b1fc7982d996b96c92f8172dbbc3875fdccd
  Author: Vaclav Petras <wenzeslaus at gmail.com>
  Date:   2020-01-30 (Thu, 30 Jan 2020)

  Changed paths:
    M CONTRIBUTING.md

  Log Message:
  -----------
  Issues are now on GitHub (#315)

This removes the Trac Ticket instructions and adds GitHub issues.
The link goes to templates like the New issue button on GitHub.
The old issues on Trac are not mentioned for simplicity
and it is up to the community (not the reporter)
to identify and migrate any duplicates.