Add Mobility page for ISBs, MRT info

[kagiura]

https://github.com/kagiura/nusmods/tree/kagiura/mobility

TODO:
immediate:

• replace with proxy API url
• placeholders for when no bus data / no buses left today
• svc E placeholder (make it show "resumes later today")
• actually make it register if its term or holiday (in getServiceStatus (src/utils/mobility.ts))
• update bus schedule
• button to switch to opposite side stop
• directional arrows for one way svc
• optimize: use useCallback/useMemo
• auto-switch to BTC when needed (and vice versa)
• fix text font size for selected/focused stop

future:

• show KR / BG MRT timings too why not
• make it just use a normal polyline so its easier (?) to update when route changes
• locate nearby classrooms

[kagiura]

refactored a fck ton + this shows properly whether there actually is no more buses or there was an error

[kagiura]

(also, its kind of annoying to take out the keys manually every time i wanna commit so ill wait until proxy api is set up before i continue with timings-related features haha)

[kagiura]

(minor update: MRT timings do not exist as a public api in singapore :,)

[kagiura]

optimization checklist

• MobilityContainer
• SvcDetail
• SvcList
• StopDetail
• LocationMap
• ISBServices