Add support for Marker GeoCharts and ISO-3166:2 district codes

[alexandre97costa]

Would you like to work on this feature?

• Check this if you would like to implement a PR, we are more than happy to help you go through the process.

What problem are you trying to solve?

I was trying to make a Marker GeoChart with this package, but it seems you only have support for Region GeoCharts. Furthermore, I wanted to define a region to be a single district in my country, not the country itself, but its also not possible. When the region option is passed with "PT", it renders successfully; when its "PT-18" the chart fails to render.

"PT-18" is the ISO standard for a specific district, according to wikipedia.

Describe the solution you'd like

• A value you can pass in the options object to define the type of GeoChart to render - either Region or Marker, defaults to region.

Describe alternatives you've considered

None

Documentation, Adoption, Migration Strategy

No response