title: How to add openvidu-java-client in gradle project
body: <p>I am tring to add <code>openvidu-java-client</code> to an existing multi-module <code>gradle</code> project but I get the following error :</p>
  <pre><code>Errors occurred while build effective model from /Users/xxxx/.gradle/caches/modules-2/files-2.1/io.openvidu/openvidu-java-client/2.20.0/d1b4db33036a286e7eeec5ece212c07e74417e60/openvidu-java-client-2.20.0.pom:
  'dependencies.dependency.version' for com.google.code.gson:gson:jar must be a valid version but is '${version.gson}'. in io.openvidu:openvidu-java-client:2.20.0
  'dependencies.dependency.version' for org.slf4j:slf4j-api:jar must be a valid version but is '${version.slf4j}'. in io.openvidu:openvidu-java-client:2.20.0
  Errors occurred while build effective model from /Users/xxxx/.gradle/caches/modules-2/files-2.1/io.openvidu/openvidu-java-client/2.20.0/d1b4db33036a286e7eeec5ece212c07e74417e60/openvidu-java-client-2.20.0.pom:
  'dependencies.dependency.version' for com.google.code.gson:gson:jar must be a valid version but is '${version.gson}'. in io.openvidu:openvidu-java-client:2.20.0
  'dependencies.dependency.version' for org.slf4j:slf4j-api:jar must be a valid version but is '${version.slf4j}'. in io.openvidu:openvidu-java-client:2.20.0
  </code></pre>
  <p>I am kind of new with <code>gradle</code> here is my <code>build.gradle</code> file :</p>
  <pre><code>repositories {
      mavenCentral()
  }
  
  dependencies {
      implementation 'io.openvidu:openvidu-java-client:2.20.0'
  }
  
  bootJar {
      enabled = false
  }
  
  jar {
      enabled = true
  }
  </code></pre>