Add initial Compliance doc based on features.yml Compliance features

What does this MR do?

Add a listing of compliance-enabling features with descriptions and links to docs to implement

Next step: to create the proper EE MR before we merge this.

Review app

http://review-docs-compl-vqo94z.178.62.207.141.xip.io/ce/administration/compliance.html

Related issues

https://gitlab.com/gitlab-org/gitlab-ce/issues/46477

Author's checklist

• Apply the correct labels and milestone
• Crosslink the document from the higher-level index
• Crosslink the document from other subject-related docs (N/A)
• Correctly apply the product badges and tiers (N/A)
• Port the MR to EE (or backport from CE): always recommended, required when the ee-compat-check job fails

Review checklist

• Your team's review (required)
• PM's review (recommended, but not a blocker)
• Technical writer's review (required)
• Merge the EE-MR first, CE-MR afterwards