Add multi_sorcha.py and multi_sorcha.sh example files.

[Gerenjie]

Fixes # .

Describe your changes.

Review Checklist for Source Code Changes

• Does pip install still work?
• Have you written a unit test for any new functions?
• Do all the units tests run successfully?
• Does Sorcha run successfully on a test set of input files/databases?
• Have you used black on the files you have updated to confirm python programming style guide enforcement?

[mschwamb]

Hmm...it might be under docs where we want to place this code. We probably need to have a think about this before we merge this.