feat: show destination zones for a given origin zone

[balacmi]

• This is task 9
• Clicking on an origin zone (i.e., canton, municipality) one can see what the destination zones are for all trips (out-flow)
• Clicking on a zone, one can see from which other zones people come to this zone (in-flow)
• Destination zones should be colored based on the flow
• Filters should include: mode, trip purpose, and time period configurable with a slider (15min granularity)

[MichelleChaoChen]

Similar to #8 , when the "Destination Zones" choice is selected, cantons in the map are colored based on the inflow of trips from the selected origin canton. The color is based on the transportation mode selected. I still need to add a button to switch between a canton being selected as origin or destination :)