Ensure that map info windows are always visible

[dgmstuart]

Google maps handles info windows near the edge of the page by scrolling
just enough that the whole info window is in view.

But it doesn't know about the map menu we have overlaying the left side
of the screen, so we need to do this manually:

1. get the coordinates from the click event - latLng is a property of
   the click event:

   https://developers.google.com/maps/documentation/javascript/reference/advanced-markers#AdvancedMarkerElement-Events
   https://developers.google.com/maps/documentation/javascript/reference/map#MapMouseEvent

2. Wait for the info window to become visible:

   https://developers.google.com/maps/documentation/javascript/reference/info-window#InfoWindow.visible

3. Now that it's visible we can get it's width, add half of that to
   the offset, and pan so that the marker is within the resulting
   padding.