Supplemental materials in long-term archive + optional table of contents

[leibatt]

@dylancashman In my initial review I noticed some issues to be addressed:

• REQUIRED: Please create a long-term archive for the GitHub repository and please list them in your Abstract and Required Materials Sections
  • Please see: https://www.journalovi.org/author-guide.html#non-compliant-repositories
• OPTIONAL: Please create a Table of Contents Section. (If opting out, please let me know)

[dylancashman]

• Longterm archive added at https://osf.io/65gre/ and added to README.md in bc4b7cf
• Table of contents added in 30d997f