remove city markers and import city as polygons

[lisjak]

✖️ 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: