Replace moment.js with dayjs

[jkeat]

https://github.com/you-dont-need/You-Dont-Need-Momentjs/blob/master/README.md

Moment is a bloated behemoth. I've been using dayjs instead. I think the only thing you guys use moment for that dayjs doesn't support yet is the list of timezones. Which you could just grab and put in a json file

Originally posted by @austinhallock in #408 (comment)