Set up redirects from old versions of resources

[erika-tyagi]

Need to set up redirects and add a note to each README indicating that everything has moved to this repo.

• [x] https://ui-research.github.io/urbngit
• [x] https://ui-research.github.io/urbngit/confidential-data-and-git.html
• [x] https://ui-research.github.io/code-library/github/github.html
• [x] https://ui-research.github.io/virtual-envs