chore(explorer): enable CORS for /api endpoints

[JuArce]

Enable CORS for /api endpoints

Description

The new website uses the api/verified_batches_summary endpoint from the explorer. This endpoint needs to have enabled CORS. If not, the client browser is blocked and cannot get the data.

Type of change

• Bug fix

Checklist

• “Hotfix” to testnet, everything else to staging
• Linked to Github Issue
• This change depends on code or research by an external entity
  • Acknowledgements were updated to give credit
• Unit tests added
• This change requires new documentation.
  • Documentation has been added/updated.
• This change is an Optimization
  • Benchmarks added/run
• Has a known issue
  • Link to the open issue addressing it
• If your PR changes the Operator compatibility (Ex: Upgrade prover versions)
  • This PR adds compatibility for operator for both versions and do not change batcher/docs/examples
  • This PR updates batcher and docs/examples to the newer version. This requires the operator are already updated to be compatible