[Feauture] Better support for IndexSeries

[CodyCBakerPhD]

Two examples of IndexSeries in this file

https://flatironinstitute.github.io/neurosift/?p=/nwb&url=https://api.dandiarchive.org/api/assets/5fe35951-5480-4fd0-94f8-7b139c994c9e/download/&dandisetId=000728&dandisetVersion=draft&tab=neurodata-item:/stimulus/presentation/natural_movie_one_stimulus|IndexSeries

The data of an IndexSeries are the indices into the linked indexed_timeseries (in this instance, a grayscale ImageSeries with 10MB chunks and roughly 3:1 compression) or indexed_images (right now somewhat inefficient as a collection of datasets, each one for an image, roughly 1MB; related #125)

The timestamps (could also have start time + rate, no example of that though) are the usual timing information for when each stimulus was presented

As is, the rendering appears as a default TimeSeries of these quantities (data index values over time; showing how in my case the indices reset as the same templates are reshown over time)

But here an alternative view of the main data (or joint view together with its template, which I cannot currently do a joint selection of) could instead display the target of the link; the movie or image at a particular point in time