add small borders to basins

src/assets/images/P_Aquaculture_effluents_map.png

src/assets/images/P_Industrial_effluents_map.png

src/assets/images/P_Mining_map.png

src/assets/images/P_Oil_or_gas_exploration_map.png

src/assets/images/P_Pharmaceuticals_map.png

src/assets/images/P_Plastics_map.png

src/assets/images/P_Urban_wastewater_map.png

src/assets/images/Pollution_map.png