Add Map/Challenge Tags

[viddie]

Smth like:

• Length (Short, Medium, Long)
• Input Density
• ...?

Model:

• New table tag (id, name)
• New table challenge_tag (id, challenge_id, tag_id)

Backend:

• Endpoints:
  • tag.php (get, update [v], create [v], delete [v])
  • challenge-tag.php (get, update [v], create [v], delete [v])

Frontend:

• Show as chips somewhere on challenge page
• Show somehow for all challenges in a map on the map page
• Include in search