'Challenge list' page

[Lordfirespeed]

As things stand, hackers only have access to a list of quests (on the main page).
For DurHack 2024, we created one quest which listed all available challenges and this sufficed.
It would be more ideal to create a dedicated, searchable 'challenge list' page, which lists all available challenges (even ones that do not correspond to any quest).
implementation would be very similar to the existing volunteer challenge list.