Better support for custom Nightscout URLs

[aleb]

As per #51 (comment), the custom Nightscout URL must have the following template:

https://{DOMAIN}:{PORT}/pebble?token={TOKEN}&count=47

This is ridiculously difficult to figure out. The documentation at https://glancewatchface.com/#setup gives the "https://glancedata.herokuapp.com/pebble" example which is confusing. It should explain where "pebble" is coming from, or give other examples.

The UI does not have any note about what URL is valid, or how to check that it's correct.

Note, currently if you specify a token in the URL and miss the &count=47 part, which is not specified in the wizard page, it's added automatically but in a wrong way. The final URL looks like https://.../pebble?token=...?count=47 (note the two question marks), and it's invalid.

[ddellspe]

This was actually added in #199 and has some further improvements in #200 unfortunately it hasn't been released yet (likely because both @Rytiggy and I no longer use Fitbits ourselves.

[milesressler]

@ddellspe @Rytiggy Are you guys still planning to maintain this project? I have a Sense 2 and am getting the E404 issue as well using a private Nightscout server (on Northflank), and wanted to check if I can help get these latest improvements released? I wouldn't mind doing some dev work to fix issues that popup as well, or if you're looking to release the project completely, that's an option as well.

I'm really bummed about not being able to see my numbers on my FitBit, and this seems like the watchface recommended everywhere I've checked, I'm sure the community would love to see it continue.

[Rytiggy]

Hey @milesressler I've had very little time to work on it, but I am still maintaining it, I would love any help! How would you like to contribute?