"Build Horizon" conceptual article

[SharpRake]

What topic are you requesting a resource about?

• Chainguard product
• Open source related
• Conceptual security related
• Other (please describe)

Proposed title:

Understanding Build Horizons

Description:

@amouat mentioned that we might benefit from having an article on build horizons to go with our other conceptual resources. I think it could be more or less a rehash of this blog post from January: https://www.chainguard.dev/unchained/conquer-your-build-horizon-with-chainguard-enforce-in-2023

[ltagliaferri]

Maybe we can add a section on this in the "keeping images up to date" tutorial
We also have a policy doc about build horizons: https://edu.chainguard.dev/chainguard/chainguard-enforce/policies/other-policies/maximum-image-age-policy/