Add SonarCloud analysis

pom.xml

@@ -54,6 +54,11 @@
         <annotation-api.version>1.3.2</annotation-api.version>
         <system-rules.version>1.19.0</system-rules.version>
         <urm.version>1.4.8</urm.version>
+        <!-- SonarCloud -->
+        <sonar.host.url>https://sonarcloud.io</sonar.host.url>
+        <sonar.organization>iluwatar</sonar.organization>
+        <sonar.projectKey>iluwatar_java-design-patterns</sonar.projectKey>
+        <sonar.projectName>Java Design Patterns</sonar.projectName>
     </properties>
     <modules>
         <module>abstract-factory</module>
@@ -400,6 +405,11 @@
                         </execution>
                     </executions>
                 </plugin>
+                <plugin>
+                    <groupId>org.sonarsource.scanner.maven</groupId>
+                    <artifactId>sonar-maven-plugin</artifactId>
+                    <version>3.7.0.1746</version>
+                </plugin>
             </plugins>
         </pluginManagement>