Added the Get Charge State API

[JSkimming]

https://timdorr.docs.apiary.io/#reference/vehicles/state-and-settings/charge-state

[codecov]

Codecov Report

Merging #8 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master     #8    +/-   ##
======================================
  Coverage     100%   100%            
======================================
  Files          12     13     +1     
  Lines         396    537   +141     
  Branches       58     69    +11     
======================================
+ Hits          396    537   +141

Impacted Files	Coverage Δ
src/Tesla.NET/Models/ChargeState.cs	100% <100%> (ø)
src/Tesla.NET/Requests/HttpClientExtensions.cs	100% <100%> (ø)	⬆️
src/Tesla.NET/TeslaClient.cs	100% <100%> (ø)	⬆️

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