SonarQube: add tag `alpine`

library/sonarqube

@@ -4,5 +4,6 @@
 latest: git://github.com/SonarSource/docker-sonarqube@06fcdc6ef062f43a5513bd327a79e7c5011fb0a3 5.6.1
 lts: git://github.com/SonarSource/docker-sonarqube@06fcdc6ef062f43a5513bd327a79e7c5011fb0a3 5.6.1
 5.6.1: git://github.com/SonarSource/docker-sonarqube@06fcdc6ef062f43a5513bd327a79e7c5011fb0a3 5.6.1
+alpine: git://github.com/SonarSource/docker-sonarqube@06fcdc6ef062f43a5513bd327a79e7c5011fb0a3 5.6.1-alpine
 lts-alpine: git://github.com/SonarSource/docker-sonarqube@06fcdc6ef062f43a5513bd327a79e7c5011fb0a3 5.6.1-alpine
 5.6.1-alpine: git://github.com/SonarSource/docker-sonarqube@06fcdc6ef062f43a5513bd327a79e7c5011fb0a3 5.6.1-alpine