Update the battery example to match the spec
Update the battery example to match the spec

Uses the `navigator.getBattery()` promise when available instead of the deprecated `navigator.battery`
memezilla/simpl,gtrdotmcs/simpl,SarahCheaib/simpl,calderaro/simpl,memezilla/simpl,ptool/simpl,mauricionr/simpl,nishartm/simpl,calderaro/simpl,gtrdotmcs/simpl,SarahCheaib/simpl,mportuesisf/simpl,bolabola/simpl,mauricionr/simpl,staskh/simpl,austad/simpl,DigitalCoder/simpl,mportuesisf/simpl,samdutton/simpl,snake0zero/simpl,austad/simpl,mvenkatesh431/simpl,ptool/simpl,mauricionr/simpl,staskh/simpl,nishartm/simpl,snake0zero/simpl,snake0zero/simpl,memezilla/simpl,mvenkatesh431/simpl,austad/simpl,samdutton/simpl,gtrdotmcs/simpl,bolabola/simpl,DigitalCoder/simpl,mvenkatesh431/simpl,ptool/simpl,staskh/simpl,SarahCheaib/simpl,DigitalCoder/simpl,nishartm/simpl,bolabola/simpl,calderaro/simpl