Update main FAQ

[scott-klaytn]

Proposed changes

Revamp the main FAQ and add it back to sidebar navigation

Types of changes

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

• Minor Issues and Typos
• Major Content Contribution
• Others

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 reach out. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• I have read the CONTRIBUTING GUIDELINES
• I have read the CLA and signed by comment I have read the CLA Document and I hereby sign the CLA in first time contribute
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

Related issues

Further comments