Transition from 'moment' to 'luxon' due to deprecation

[majesticio]

The moment library has been considered deprecated for a while now. With that in mind, we've decided to switch to the luxon library for our project's date and time handling.

luxon offers several benefits over moment, including:

• Immutable objects, which reduce the risk of bugs and improve readability
• Better performance, particularly in parsing and formatting
• Simpler API with fewer gotchas
• Built-in support for the Intl API, which provides better localization options

We will be updating the codebase to replace moment with luxon for openaq-fetch.