Fendl 3.2 preliminary release

[shimwell]

There is a preliminary release of FENDL 3.2 on the IAEA website https://www-nds.iaea.org/fendl_library/preliminary/

So I've started adding the new nuclear data to the release details of the convert_fendl.py script on this branch

https://github.com/openmc-dev/data/tree/adding_fendl_3.2

I can finish this once the release moves out of the preliminary stage.

[shimwell]

Solved in pr #58