Checkstyle integration

[arcticicestudio]

Has to be done and merged before #17

Integrate Checkstyle into the development stack to comply with the Java Code Style Guide version 🏷️ 0.1.0.

The target version of the style guide configuration for Checkstyle is 8.0 which must be override the default version 6.11.2 of the latest maven-checkstyle-plugin version 2.17.

      <!-- .... -->
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-checkstyle-plugin</artifactId>
        <dependencies>
          <dependency>
            <groupId>com.puppycrawl.tools</groupId>
            <artifactId>checkstyle</artifactId>
            <version>${checkstyle.version}</version>
          </dependency>
        </dependencies>
        <!-- .... -->
      </plugin>

The documentation will be added in #10 and #11.