Create option for dynamic time range on timeline

[breezykermo]

Continuing the conversation from this PR on a fork of timemap, we would be interested in the following feature for timemap:

• Create an option for app.timeline.range in the redux store to always open up the timeline state on 'today' (wherever/whenever the user if viewing the application), rather than only being able to "hard-code" a range. This is more suitable for timemap instances that are updated on a day-to-day basis, such as https://ukraine.bellingcat.com.

@hgrsd in order to integrate this into the upstream we would need it to be backwards-compatible with the old format for specifying ranges. I am not picky about how we do this; it could be as simple as allowing app.timeline.range to be either a list or an object, and to calibrate the timeline range according to that type.