Fix shortcomings identified for obtaining CII Best Practices passing badge

[tuminoid]

This will be parent ticket for fixing the shortcomings identified during evaluating the IRSO for CII Best Practices passing badge.

• Our CII project: https://www.bestpractices.dev/en/projects/9986
• Badge addition PR: 📖 add CII badge #266

Already fixed issues:

• SECURITY CONTACTS: 📖 add missing SECURITY_CONTACTS file #264

Previously created issues:

• Releasing documentation: Document the releasing process #119

[Rozzii]

/triage accepted
/kind ci

[Rozzii]

/kind documentation

[metal3-io-bot]

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