Add code coverage in CI

[gpengzhi]

No description provided.

[ZhitingHu]

Pls add a badge to README, and do the same for TF

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@267bfd7). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #245   +/-   ##
=========================================
  Coverage          ?   83.09%           
=========================================
  Files             ?      192           
  Lines             ?    15196           
  Branches          ?        0           
=========================================
  Hits              ?    12627           
  Misses            ?     2569           
  Partials          ?        0

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[ZhitingHu]

Pls update version to 0.1.1-unreleased before making any other update to the repo