Update README.md

[riteshdg]

Fix README description with right sentinel nodes count

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@659f4ba). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master      #17   +/-   ##
=========================================
  Coverage          ?   72.81%           
  Complexity        ?      116           
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  Files             ?       20           
  Lines             ?      515           
  Branches          ?       38           
=========================================
  Hits              ?      375           
  Misses            ?      118           
  Partials          ?       22           

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