Add an example/demo notebook using the Time Horizons of Futuristic Fiction dataset

https://data.post45.org/posts/futuristic-fiction/

How hard to revisit the parsing / median approach used to publish the dataset by parsing the original dates as intervals?

Can we generate a plot similar to the one in the data essay but using multiple or range values for dates?
- when a work has multiple dates or a date range, can we split the opacity across the dots / range ?

