Missing contributing and code of conduct files

[jzonthemtn]

The readme references contributing and code of conduct files that do not exist.

• https://github.com/o19s/ubi/blob/main/CONTRIBUTING.md
• https://github.com/o19s/ubi/blob/main/code_of_conduct.md

[epugh]

Thanks for opening this up... Part of me almost wants to skip fixing it till we figure out governance better, but since we reference it...