Add option to choose which visualisations to generate

[hugovk]

By default, all the visualisations are generated when running the CLI.

Sometimes though, I want to iterate and adjust the parameters to generate a map with a smaller bbox, or for a different time period. So I don't need to regenerate all the other files, which can be slow.

This adds an option --vis (open to another name).

By default, it will generate all.

Or you can give --vis map to just generate the map, or give multiple like --vis map facets landscape.

Also gives some example CLI use right at the top of the README.

[hugovk]

This adds an option --vis (open to another name).

Maybe --select?