Replace momentjs with dayjs where possible

[majakomel]

Related issue: #510

Also fixes an issue with inconsistent time display - described in: #515

Initially, I intended to go with date-fns, but unfortunately it doesn't have a nice interface to work with timezones/utc and it required working a lot with the native Date object, which defeats the purpose of a library altogether. After a bit of exploration and testing, I decided to go with day.js, which is very lightweight, just as popular, and with a very similar interface as momentjs - which makes it also easy to replace.

Unfortunately, it's not possible to get rid of moment.js completely just yet since the Datetime component depends on it. I will follow up with this issue, to replace it with a date-library-agnostic component and remove the use of momentjs completely in another PR.

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[hellais]

Thanks for putting this together!

Left a comment on something that should be addressed prior to merge.

Also, while you are touching this bit of the codebase, perhaps you can also integrate a fix for this bug: #515 (comment)?

[majakomel]

Thanks for the review @hellais, I fixed the issue with the timezone and inconsistent time display, can you check again if things are as expected?

[hellais]

I did some testing of the branch and it works great.

I left 2 very minor comments in the PR, which once addressed we can merge it.

Thanks for putting this together!

[hellais]

Yes this looks great. Thanks for putting it together!

I am going to proceed with merging it.