add codecov badge

[HarrisChu]

No description provided.

[codecov-commenter]

Codecov Report

Merging #352 (a1251e6) into master (287f67a) will not change coverage.
The diff coverage is n/a.

❗ Current head a1251e6 differs from pull request most recent head 67d7cb4. Consider uploading reports for the commit 67d7cb4 to get more accurate results

@@            Coverage Diff            @@
##             master     #352   +/-   ##
=========================================
  Coverage     62.17%   62.17%           
  Complexity      606      606           
=========================================
  Files            55       55           
  Lines          2826     2826           
  Branches        396      396           
=========================================
  Hits           1757     1757           
  Misses          793      793           
  Partials        276      276           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 287f67a...67d7cb4. Read the comment docs.