[Feature] Make possible to use string values on Geo/Map instead of only using numbers

[mas-oliveira]

What problem does this feature solve?

This feature will allow to put some information on country labels.

What does the proposed API look like?

Prepare params to apply an onString method, or create a field in data to receive string values.

[github-actions]

This issue has been automatically marked as stale because it did not have recent activity. It will be closed in 7 days if no further activity occurs. If you wish not to mark it as stale, please leave a comment in this issue.

[github-actions]

This issue has been automatically closed because it did not have recent activity. If this remains to be a problem with the latest version of Apache ECharts, please open a new issue and link this to it. Thanks!