Add criteria for gating by asset type

Why is this change being made?

I created this MR to add a section for gated content criteria so everyone is on the same page about what type of assets get gated vs. not per this issue.

@jgragnola @erica @jjcordz Please review/approve and add any commits before merging.

Does this MR meet the acceptance criteria?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what