fix: Update cert instructions for NGINX One Console

[mjang]

Proposed changes

Problems:

Lack of clarity in certificates. NGINX supports certificates in three categories:

• Website traffic (typically purchased from a CA)
• Repo verification
• F5 License verification

Similar processes for adding / editing certs in an Instance / Config Sync Group

Clarification needed on the types of certs that are supported

Solution:

• Added table for different categories of certs
• Added more detailed description of different types of supported certs
• Set up
  • Distinct files for adding / including certs for both instances and Config Sync Groups
    • content/nginx-one/how-to/nginx-configs/add-file.md
    • content/nginx-one/how-to/config-sync-groups/add-file-csg.md
  • Includes for common content (see files in the content/includes/nginx-one/add-file directory)

Closes #76

Checklist

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• I have signed the F5 Contributor License Agreement (CLA)

• If applicable, I have added tests that prove my fix is effective or that my feature works

• If applicable, I have checked that any relevant tests pass after adding my changes

• I have updated any relevant documentation (README.md and CHANGELOG.md)

• I have rebased my branch onto main

• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

• If the change involves:

  • Code
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[github-actions]

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[ADubhlaoich]

Generally LGTM, added edit suggestions for some Hugo formatting/file style things.