Added Unit test and Code Coverage report for all platforms

[dreampiggy]

Thanks :

• SwiftUI-Introspect
• ViewInspector

This close #45

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@91f81c5). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master      #74   +/-   ##
=========================================
  Coverage          ?   43.81%           
=========================================
  Files             ?        9           
  Lines             ?      671           
  Branches          ?        0           
=========================================
  Hits              ?      294           
  Misses            ?      377           
  Partials          ?        0

Flag	Coverage Δ
#ios	43.81% <ø> (?)

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