Fix to support JPMS

[OpenHelios]

This is a fix for #332.

This change needs to update the dependency of logback-classic from 1.2.13 to 1.3.15, because 1.3.x is the first version, which supports JPMS, i.e. it includes the needed module-info file.

Only in the main project ecs-logging-core and in logback-ecs-encoder the module-info file has been added. Also in jul-ecs-formatter and log4j-* projects a module-info file could be added in a similar way.

[cla-checker-service]

💚 CLA has been signed

[OpenHelios]

The process to sign the contributor agreement does not work for me https://www.elastic.co/contributor-agreement Only the progress bar runs to end, but nothing more happens.

[SylvainJuge]

The process to sign the contributor agreement does not work for me https://www.elastic.co/contributor-agreement Only the progress bar runs to end, but nothing more happens.

The commits are using [email protected] as email adress, I am not 100% sure but this might be the issue here, could you try to use your non-anonymous email address here ?

[OpenHelios]

I gave the signing process an other try by pushing the commits with my real email address. With Chromium and not with Firefox I was able to start the signing process, but at the end after clicking "Finish" I get the error message "apps.docusign.com hat die Verbindung abgelehnt.", which means translated to English, that the connection was rejected. What am i missing?
Now signing was successful.