Make page for best practices tiers

[covesturtevant]

Topics often span multiple tiers (e.g. commenting code vs. automatic documentation) Add different emojis in the individual resources guide pages to indicate which Best Practice Tier it belongs to. Then the Best Practices Page can describe what the flags mean and link to specific sections, e.g. Name of Page#Name of section

[jemissik]

You can create labels for page sections to make cross-referencing easier (and then the references won't break if section headers are edited): https://jupyterbook.org/en/stable/tutorials/references.html