Expand coding standards

[davidmirror-ops]

According to the OpenSSF Best Practices requirement around basic website content:

The information on how to contribute SHOULD include the requirements for acceptable contributions (e.g., a reference to any required coding standard

But currently, CONTRIBUTING only mentions Logging and Error Handling.

In order to meet this requirement, an expanded section on Coding Standards should be created to better guide new contributors.

See example here