multiple countdown timers

[henrylin03]

as a user, i can input, view, and remove multiple countdown timers so that i can track different competitions

[henrylin03]

for inspiration, can be done in react.js using hooks: https://www.codecademy.com/courses/react-101/lessons/the-state-hook/exercises/why-use-hooks

however, this would require migrating project to react

[henrylin03]

now migrated to react/mantine ui library, can use mantine's scroll-area component per design doc