Implement Map Comparison Widget

[aboydnw]

Context

Followup to designs from #1178
This does NOT include the ability to open in a full page, that will be in a followup ticket to designs in #1261

Goal is to update the map comparison widget used in stories and dataset overview pages to allow for comparison of different datasets. These designs should also apply to other map comparisons though.

1. Same date, different dataset
2. Same dataset, different date
3. Different date, different dataset? (optional)

Acceptance Criteria

• MDX files can be configured with a map comparison showing two different datasets, and the resulting map matches designs in [Design] Map Comparison for Two Datasets #1178 (except no need for the "Open" button, yet)
• MDX files can be configured with a map comparison showing the same dataset with two different dates, and the resulting map matches designs in [Design] Map Comparison for Two Datasets #1178