message: Add matrix badge
diff: ## user manual and guide
  -[![Github-CI](https://github.com/freebayes/freebayes/workflows/CI/badge.svg)](https://github.com/freebayes/freebayes/actions) [![Travis-CI](https://travis-ci.com/freebayes/freebayes.svg?branch=master)](https://travis-ci.com/freebayes/freebayes) [![AnacondaBadge](https://anaconda.org/bioconda/freebayes/badges/installer/conda.svg)](https://anaconda.org/bioconda/freebayes) [![DL](https://anaconda.org/bioconda/freebayes/badges/downloads.svg)](https://anaconda.org/bioconda/freebayes) [![BrewBadge](https://img.shields.io/badge/%F0%9F%8D%BAbrew-freebayes-brightgreen.svg)](https://github.com/brewsci/homebrew-bio) [![GuixBadge](https://img.shields.io/badge/gnuguix-freebayes-brightgreen.svg)](https://www.gnu.org/software/guix/packages/F/) [![DebianBadge](https://badges.debian.net/badges/debian/testing/freebayes/version.svg)](https://packages.debian.org/testing/freebayes)
  -
  +[![Github-CI](https://github.com/freebayes/freebayes/workflows/CI/badge.svg)](https://github.com/freebayes/freebayes/actions) [![Travis-CI](https://travis-ci.com/freebayes/freebayes.svg?branch=master)](https://travis-ci.com/freebayes/freebayes) [![AnacondaBadge](https://anaconda.org/bioconda/freebayes/badges/installer/conda.svg)](https://anaconda.org/bioconda/freebayes) [![DL](https://anaconda.org/bioconda/freebayes/badges/downloads.svg)](https://anaconda.org/bioconda/freebayes) [![BrewBadge](https://img.shields.io/badge/%F0%9F%8D%BAbrew-freebayes-brightgreen.svg)](https://github.com/brewsci/homebrew-bio) [![GuixBadge](https://img.shields.io/badge/gnuguix-freebayes-brightgreen.svg)](https://www.gnu.org/software/guix/packages/F/) [![DebianBadge](https://badges.debian.net/badges/debian/testing/freebayes/version.svg)](https://packages.debian.org/testing/freebayes) [![Chat on Matrix](https://matrix.to/img/matrix-badge.svg)](https://matrix.to/#/#vcflib:matrix.org)
  --------
  ## Overview
  