support pixi environment

Currently, a viable environment exists using 'conda/mamba'. NSD analysis.sns.gov machines ( where QuickPlotMR is to be run ) are transitioning to pixi for environment management.

A branch, QuickPlotMR:feature/pixi has been established to achieve this capablity.

Current issue is that pixi is not able to resolve the dependencies because Python 3.6.7 is currently the only one which resolves the dependencies and that Python is not available in pixi anymore ( it is a deprecated version )

The problems come from QT4, PIL(low) and pip:pdfreader. Divesting from pip:pdfreader ( and/or an upgrade to QT(6) ) would be viable first steps.