Add sensor markers and map interactions

[caseycesari]

Overview

Adds markers for sensors to the map. Clicking a marker transitions the map to viewport centered around the marker in anticipation of the selected marker view. A "back to map" button is also added in this view. Clicking it transitions the map back to the initial viewport.

Connects to #27

Demo

Demo gif is low-res and short due to large file size.

Testing Instructions

• Click a map marker. Verify the map zooms to that marker and that the "back to map" button appears.
• Click the "back to map" button. Verify the map returns to the initial position.

[caseycesari]

@kellyi pushed a fixup commit to address most of your comments. Mind doing another quick pass?

[kellyi]

Tested out the app and it still works! Code also looks good.