Adding ADR for using maplibre to repo (see issue #299) (#325)

* Adding ADR for using maplibre to repo (see issue #299)

docs/decisions/0007-maplibre.md

@@ -0,0 +1,67 @@
+# Use MapLibre for Map Visualization
+
+## Context and Problem Statement
+
+Styling a map with a large number of features, in a performant way, is difficult. With 200,000+ block groups, our project needs this performance for a smooth user experience. Our current mapping approach, using OpenLayers, is insufficient for this task. We propose switching to MapLibre as a free and open source way to improve the performance and user experience of our map.
+
+## Decision Drivers
+
+- Free and Open Source
+- Good performance in rendering a large number of features
+- Good performance in zooming and panning
+- Easy map styling
+
+## Considered Options
+
+- MapLibre GL JS 1.15.0
+- Mapbox GL JS 2.3.1
+- Mapbox GL JS 1.13.0
+- OpenLayers 6.4.3
+
+## Decision Outcome
+
+Chosen option: [MapLibre 1.15.0](https://github.com/maplibre/maplibre-gl-js), a free and open-source library with good performance and standard map styling capabilities, and continued development lifecycle.
+
+### Positive Consequences
+
+- MapLibre is free and open source
+- Performance is preferable to OpenLayers, as seen in this video: [MapLibre Performance](./0007-files/MapComparison.mp4)
+- MapLibre is under continued development
+
+### Negative Consequences
+
+- The MapLibre project is still relatively new
+  - Mitigation: if we need to revert we can go back to Mapbox 1.13.0
+- We need to change variable and class names to change "mapbox" references to "maplibre"
+  - Mitigation: this is a relatively small change
+- There might be other incompatibilities with mapbox and/or backwards incompatibilities as the Maplibre framework evolves
+  - Mitigation: we will follow the progress of MapLibre as it evolves
+
+## Pros and Cons of the Options
+
+### Mapbox-GL JS 2.3.1
+
+The latest released version of [Mapbox](https://docs.mapbox.com/mapbox-gl-js/api/)
+
+- Pro: performance is quite good and improving
+- Con: as of December of last year, Mapbox has moved to a proprietary license
+- Con: requires key, payment, even for self-hosted version and tiles
+
+### Mapbox-GL JS 1.13.0
+
+The last pre-license change version of [Mapbox](https://github.com/mapbox/mapbox-gl-js/releases/tag/v1.13.0)
+
+- Pro: Perf still good
+- Pro: License permissive, no required key
+- Con: Not under current active development
+
+### OpenLayers 6.4.3
+
+This option is sticking with our current choice, the latest released version of the [OpenLayers](https://github.com/openlayers/openlayers), an alternative open source framework.
+
+- Pro: No change necessary vs. current setup
+- Con: Without WebGL support, performance is inferior to these other options
+
+## Links
+
+- [Improving the Performance of Mapbox GL JS Maps](https://docs.mapbox.com/help/troubleshooting/mapbox-gl-js-performance/) - a general overview of the concerns related to mapping performance