Add missing Log4j2 plugin configuration

[yuri1969]

The example XML was missing plugin search configuration as described at:
https://logging.apache.org/log4j/2.x/manual/configuration.html#ConfigurationSyntax

Make sure that:

• You have read the contribution guidelines.
• You use the code formatters provided here and have them applied to your changes. Don’t submit any formatting related changes.
• You submit test cases (unit or integration tests) that back your changes.

[codecov]

Codecov Report

Merging #132 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #132   +/-   ##
=========================================
  Coverage     72.75%   72.75%           
  Complexity      837      837           
=========================================
  Files            60       60           
  Lines          2856     2856           
  Branches        383      383           
=========================================
  Hits           2078     2078           
  Misses          592      592           
  Partials        186      186

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[mp911de]

Thanks a lot. When was packages introduced? Right now, it works also without specifying it.

[yuri1969]

@mp911de TBH, I don't know. A direct copy&paste of the example didn't work since the Gelf appender was not recognized. Pointing the Log4j2 to the right package did the job.

[mp911de]

Cool, thank you.