add SonarCloud badge

Author: guwirth

README.md

@@ -1,7 +1,7 @@
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 | **Issue Stats** | [![Issue Stats](http://issuestats.com/github/SonarOpenCommunity/sonar-cxx/badge/pr)](http://issuestats.com/github/SonarOpenCommunity/sonar-cxx) | [![Issue Stats](http://issuestats.com/github/SonarOpenCommunity/sonar-cxx/badge/issue)](http://issuestats.com/github/SonarOpenCommunity/sonar-cxx) |
-| **SonarCloud**<br>(Technical Debt analysis) | [SonarCloud](https://sonarcloud.io/organizations/sonaropencommunity/projects) |   |
+| **SonarCloud**<br>(Technical Debt analysis) | [![Quality Gate](https://sonarqube.com/api/badges/gate?key=org.sonarsource.sonarqube-plugins.cxx:cxx)](https://sonarqube.com/dashboard/index/org.sonarsource.sonarqube-plugins.cxx:cxx) |   |
 | **Travis CI**<br>(Linux Build and Integration Tests) | [![Build Status](https://travis-ci.org/SonarOpenCommunity/sonar-cxx.svg?branch=master)](https://travis-ci.org/SonarOpenCommunity/sonar-cxx) |   |
 | **AppVeyor CI**<br>(Windows Build and Deployment) | [![Build status](https://ci.appveyor.com/api/projects/status/f6p12h9n59w01770/branch/master?svg=true)](https://ci.appveyor.com/project/SonarOpenCommunity/sonar-cxx/branch/master) | [Download](https://ci.appveyor.com/project/SonarOpenCommunity/sonar-cxx/branch/master/artifacts) |