Help existing projects learn about what the CNCF can help with

[carolynvs]

For maintainers who missed or didn't get the latest onboarding materials for the CNCF, perhaps because their projects were accepted very early on, they may not be aware of all the nice things the CNCF can do for them. Let's write up an advisory doc and mention it in some of our key templates so that they are aware

https://www.cncf.io/services-for-projects/

[justaugustus]

cc: @amye (based on today's discussion)

[aliok]

This is in "blocked" state as this requires collaboration with CNCF.

Notes:

• Stub out CNCF resources section. #599 is related, moving some content from https://www.cncf.io/services-for-projects/ to TAG website
• CNCF is currently standardizing some resources in sandbox, which could solve/help this issue
• We can publicize this kind of content as it would be very useful

cc @Riaankl to add more information.