docs: fix incorrect how to contribute link in readme

[louisnow]

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Fixes #95 🦕

[codecov]

Codecov Report

Merging #96 (2f71106) into master (1bab8e7) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master       #96   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines           95        95           
  Branches        19        19           
=========================================
  Hits            95        95           

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[github-actions]

🎉 This PR is included in version 1.10.0 🎉

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