Update README.md

[neelfirst]

As a potential contributor, I couldn't find the CLA from the main Ventilator repo's README.md. so I added in a link.

[CLAassistant]

All committers have signed the CLA.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 68.43%. Comparing base (ec1e567) to head (b31f3a8). Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1343   +/-   ##
=======================================
  Coverage   68.43%   68.43%           
=======================================
  Files          81       81           
  Lines        2829     2829           
=======================================
  Hits         1936     1936           
  Misses        893      893