remove city markers and import city as polygons

✖️ part I: data acquisition (#70)
- acquire city polygon data
- potential DB restructuring to associate oral history data with city polygon data

☑️ part II: import and display
- import city polygon data
- display cities as polygons; remove circles/points as markers for cities
- all city polygons are clickable

✖️ part III: style (#72)
- city polygons that have an associated oral history display as a red, textured polygon (see issue for more info regarding this)
- no polygon border
- city polygons that do NOT have any associated oral histories display as white with a gray border

➡️ see the 🌸 **pink 🌸 arrows and boxes** within the below image: