Opacities script with proper credit (#1682)

* Create opacities.py

* Ported over opacities script from old tardis analysis

* Black formatting

* Remove header information

Co-authored-by: Mark Magee <53613663+MarkMageeAstro@users.noreply.github.com>

Co-authored-by: Ulrich Noebauer <ulrich.noebauer@googlemail.com>