test: Add InitVar and ClassVar examples

[yukinarit]

@AustinScola
It seems InitVar and ClassVar is already supported 🙂

Closes #230

[codecov]

Codecov Report

Base: 90.79% // Head: 90.79% // No change to project coverage 👍

Coverage data is based on head (f5171fa) compared to base (4ea7504).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #280   +/-   ##
=======================================
  Coverage   90.79%   90.79%           
=======================================
  Files          10       10           
  Lines        1586     1586           
  Branches      337      337           
=======================================
  Hits         1440     1440           
  Misses        104      104           
  Partials       42       42           

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