Decide on an icon set for diagrams and create a key for icons

[abrennan89]

No description provided.

[evankanderson]

Someone from RedHat provided a set of icons a few years back for IDE purposes:

https://github.com/knative/community/tree/main/icons

[abrennan89]

Tbh I feel like those are a bit over-complicated and not really intuitive. I'd like to see us use something more simple, but if the general consensus is that folks are happy with those, I guess we could use them.

Could we transfer this issue to the community repo maybe and have the TOC decide? Whatever we choose should be used consistently I think, so it would be good to have the decision more visible than just the docs WG.

[github-actions]

This issue is stale because it has been open for 90 days with no
activity. It will automatically close after 30 more days of
inactivity. Reopen the issue with /reopen. Mark the issue as
fresh by adding the comment /remove-lifecycle stale.