Add a new build prefix for "creating" an artifact, separate from updating

[nixjdm]

Currently when you build a site, if an artifact is created, and didn't exist before, it gets a "U" for being updated. This is the same as if the artifact changed. I propose a new artifact specifically for creating or adding an artifact where it didn't exist before. This will help visually separate the two, in my mind, conceptually different events.

C index.html

rather than the current

U index.html