Add download data button for RGB++ chart

[Keith-CY]

Is your feature request related to a problem? Please describe.
In other charts, there's a download data button to get a CSV file.

But the chart of RGB++ doesn't

Describe the solution you'd like
Add a download data button at the top right corner of the chart to generate a CSV file.

Additional context
This feature request comes from the marketing team.

[Keith-CY]

I'll update it today

[Keith-CY]

Should be updated by nervosnetwork/ckb-explorer-frontend@be766a0

[Keith-CY]

updated on testnet