Add codecov support

[mszostok]

Description

Changes proposed in this pull request:

• Add codecov support

Related issue(s)

• Add test coverage to internal pkg #14

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@a07509e). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master      #38   +/-   ##
=========================================
  Coverage          ?   83.33%           
=========================================
  Files             ?        2           
  Lines             ?       48           
  Branches          ?        0           
=========================================
  Hits              ?       40           
  Misses            ?        7           
  Partials          ?        1           

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