serve tutorial pdfs

[hkershaw-brown]

To do:

Needs updating:

• website https://dart.ucar.edu/tutorials/
• docs: https://github.com/NCAR/DART/tree/main/guide/DART_LAB
• docs: https://github.com/NCAR/DART/tree/main/theory

This repo:

• add pdfs
• index page
• directory for building blocks