Add Battery indicator for chooser main screen

[greatjack1]

Can we add a battery indicator to the main chooser screen?

[thedicemaster]

I don't think it would be of much use.
power measurement is incredibly inaccurate to the point that the pocketsprite can only really tell "full" "almost empty" and "somewhere in between".
it would display either 100%, 1%, or ??%.

besides, there's already an always visible indicator that warns you if the battery is getting low.

[rorosaurus]

This was also requested on discord. I think I'll take a stab at it when time permits. There's an API we can call to estimate the battery usage, but like dicemaster says, it's not going to be very accurate.
Separately, I think I'll try to take a stab at making that estimate more accurate by approximating the discharge curve, instead of assuming a linear relationship between voltage and SOC.

[rorosaurus]

PocketSprite/8bkc-sdk#15

[rorosaurus]

If we made the change in the sdk, in kcugui_filechooser_filter(), we could get this battery indicator in all the emulator "select ROM" screens as well.

[rorosaurus]

PR here: #18

[rorosaurus]

3rd time's a charm... #20

[rorosaurus]

@thedicemaster there are some things we can do to be much more accurate with our battery estimation. more info: PocketSprite/8bkc-sdk#15