docs: add some additional badges
Added badges for weekly downloads, docs build status, gitter and matrix
chat.
RDFLib
======
[![Build Status](https://github.com/RDFLib/rdflib/actions/workflows/validate.yaml/badge.svg?branch=master)](https://github.com/RDFLib/rdflib/actions?query=branch%3Amaster)
+[![Documentation Status](https://readthedocs.org/projects/rdflib/badge/?version=latest)](https://rdflib.readthedocs.io/en/latest/?badge=latest)
[![Coveralls branch](https://img.shields.io/coveralls/RDFLib/rdflib/master.svg)](https://coveralls.io/r/RDFLib/rdflib?branch=master)
+
[![GitHub stars](https://img.shields.io/github/stars/RDFLib/rdflib.svg)](https://github.com/RDFLib/rdflib/stargazers)
+[![Downloads](https://pepy.tech/badge/rdflib/week)](https://pepy.tech/project/rdflib)
[![PyPI](https://img.shields.io/pypi/v/rdflib.svg)](https://pypi.python.org/pypi/rdflib)
[![PyPI](https://img.shields.io/pypi/pyversions/rdflib.svg)](https://pypi.python.org/pypi/rdflib)
+
[![Contribute with Gitpod](https://img.shields.io/badge/Contribute%20with-Gitpod-908a85?logo=gitpod)](https://gitpod.io/#https://github.com/RDFLib/rdflib)
+[![Gitter](https://badges.gitter.im/RDFLib/rdflib.svg)](https://gitter.im/RDFLib/rdflib?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
+[![Matrix](https://img.shields.io/matrix/rdflib:matrix.org?label=matrix.org%20chat)](https://matrix.to/#/#RDFLib_rdflib:gitter.im)
RDFLib is a pure Python package for working with [RDF](http://www.w3.org/RDF/). RDFLib contains most things you need to work with RDF, including:
