Add KIP-287: Permissionless Staking Policy

[hyeonLewis]

Proposed changes

This PR adds new KIP-287: Permissionless Staking Policy.

Types of changes

Please put an x in the boxes related to your change.

• Bugfix
• KIP Proposal
• KIP Improvement

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• Used the suggested template: https://github.com/kaiachain/KIPs/blob/main/kip-template.md
• I have read the CLA and signed by comment I have read the CLA Document and I hereby sign the CLA in first time contribution
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

Related issues

• Please leave the issue numbers or links related to this PR here.

Further comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you proposed and what alternatives you have considered, etc.

[hyunsooda]

LGTM