Add Publication for Transport-independent depletion.

[yardasol]

Description

This PR adds reference to the recently published paper detailing the Transport independent depletion feature.

Checklist

• I have performed a self-review of my own code
• I have run clang-format (version 15) on any C++ source files (not applicable)
• I have followed the style guidelines for Python source files (if applicable)
• I have made corresponding changes to the documentation (if applicable)
• I have added tests that prove my fix is effective or that my feature works (not applicable)

[paulromano]

Thanks for suggesting this change @yardasol. However, we stopped updating this list about 5 years ago because there are simply too many papers to keep track of. I normally post OpenMC-related publications here. We also have a CITATION.cff file in the repository that indicates to users the preferred citation for the code.

[yardasol]

@paulromano makes sense. I've replied with to that thread with a link to the paper!