Add repo archive notification

[scott-klaytn]

Proposed changes

• Delete temporarily added kaia tech document because it has been reflected to docs.kaia.io from kaia docs repo
• Add klaytn doc repo archive notificaiton

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• Minor Issues and Typos
• Major Content Contribution
• Others

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• I have read the CONTRIBUTING GUIDELINES
• I have signed the CLA
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

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