Add ToC to README

using doctoc

TOC entries with images need to be manually repaired,
https://github.com/thlorenz/doctoc/issues/73

README.md

+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
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+**Table of Contents**  *generated with [DocToc](https://github.com/thlorenz/doctoc)*
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+- [Cockatrice](#cockatrice)
+- [Get Involved [![Gitter chat](https://badges.gitter.im/Cockatrice/Cockatrice.png)](https://gitter.im/Cockatrice/Cockatrice)](#get-involved-)
+- [Community Resources](#community-resources)
+- [Translation Status [![Cockatrice on Transiflex](https://ds0k0en9abmn1.cloudfront.net/static/charts/images/tx-logo-micro.646b0065fce6.png)](https://www.transifex.com/projects/p/cockatrice/)](#translation-status-)
+- [Building [![Build Status](https://travis-ci.org/Cockatrice/Cockatrice.svg?branch=master)](https://travis-ci.org/Cockatrice/Cockatrice)](#building-)
+- [Building servatrice Docker container](#building-servatrice-docker-container)
+- [Running](#running)
+- [License](#license)
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 # Cockatrice
 
 Cockatrice is an open-source multiplatform software for playing card games,