Feature/#7 extra scale data

[vanlooverenkoen]

Fixed #7

Includes nullsafety. (First merge nullsafety)

This should be tested before merging

[vanlooverenkoen]

I just updated the api to get the impedance value easier without always entering age, height, gender in advance.

I added the implementation to my app that I am using every day. I will let you know about my findings.

[BeMacized]

@vanlooverenkoen awesome! If it turns out to work well enough for you for it to come out of draft state, I'd be happy to merge this.

[vanlooverenkoen]

Alright perfect

[vanlooverenkoen]

Data from the xiaomi scale app:

Data from my app with this pull request:

[vanlooverenkoen]

That looks very promising :)

[vanlooverenkoen]

Data from the mi scale app (day 2)

Data from my app (day 2)

[vanlooverenkoen]

I am using wrong formatting in some places. But that is only the implementation of my app. The values it self have a lot more decimals. So the mi scale app values look identical when using the same formatting

[vanlooverenkoen]

Again today, perfect match between my values & the mi scale values

[BeMacized]

Everything's been updated, merged, and published under 2.2.0. Thanks a lot @vanlooverenkoen!