Create `cncf` directory to share maintainers CNCF-related activities and resources

[yada]

This issue proposes creating a new directory named cncf in the Microcks community repository.

The main goal is to more broadly share with the community the activities, materials, and resources that the maintainers have created or are currently working on in the context of the CNCF. This includes work done to align Microcks with CNCF expectations, processes, and best practices.

This directory would help:

• Make visible some of the background work done by maintainers related to CNCF engagement.
• Centralize documents and resources useful for adopters and contributors (e.g., submissions, reviews, guidelines, references).
• Provide a welcoming place for community members to contribute ideas, feedback, and improvements.
• Enable collaborative maintenance of some of these resources to keep them accurate and up to date.
• Support the creation of new shared resources when needed.

The intent is to keep this content open, transparent, and community-driven.

Tasks (not limited to, and starting with:

• Create the cncfdirecty
• Create README.md in the cncfdirectory
• Copy Microcks sandbox application resource (as archive)
• Copy Microcks self-security assessment resource (to keep accurate)
• Copy Microcks GTR (General Technical Review) resource for incubation application (WIP, feedback welcome and to keep accurate)
• Link, intro the Microcks incubation application resource (WIP, feedback welcome)
• Misc, add your ideas, needs... we may link or add some CNCF initiative that are relevant here TBD