Add two Radiation Physics PDF files

[kadhirash]

What does this PR do?

Add Resources

For resources

Description

1. Radiation and particle detectors from the University of Turku
2. Radiation Physics for Personnel and Environmental Protection from the Fermi National Accelerator Laboratory

   Why is this valuable (or not)

   Two great resources from reputable areas.

   How do we know it's really free?

   Both links are pdf files of the resources!

   For book lists, is it a book?

   Yes

   Checklist:

   • [x] Not a duplicate
   • [x] Included author(s) if appropriate
   • [x] Lists are in alphabetical order
   • [x] Needed indications added (PDF, access notes, under construction)

[eshellman]

Thanks, and welcome to free-science-books!