Replace/remove momentjs library

According to [some articles](https://inventi.studio/en/blog/why-you-shouldnt-use-moment-js), momentjs is a slow/heavy/hard to debug library, and 2020's web projects should not rely on this library.
Performing a quick search on the project, it seems the momentjs is mainly used to calculate time ranges, before/after verifications, calculate time offset, and format dates. [Most of these operations( except formatting) can be done using the native elements](https://github.com/you-dont-need/You-Dont-Need-Momentjs#feature-parity).

Please evaluate if we can replace or remove momentjs from the time-tracker-ui's dependencies.