Add JUnit report parser

[n-peugnet]

I am currently trying to add this great action to my github workflow and I'm glad it can easily handle multiple reports and multiple formats. I would like to report PHPUnit's results which produces a JUnit format xml file but I got this error.

dev.gtierney.analysispublisher.reporting.collector.ReportCollectorException: Can't find a parser for 'junit' reports

I then saw on you release page that junit was not yet supported. JUnit report is a widely used report format for test runners so it would be a great addition to this action.