Add kendall tau metric

[tomcarter23]

Add the kendall tau correlation metric to collection of available metrics.

[codecov[bot]]

Codecov Report

Merging #115 (948053d) into master (03fe2e9) will decrease coverage by 0.2%. The diff coverage is 73.3%.

:exclamation: Current head 948053d differs from pull request most recent head 86a7ada. Consider uploading reports for the commit 86a7ada to get more accurate results

@@           Coverage Diff            @@
##           master    #115     +/-   ##
========================================
- Coverage    79.2%   79.1%   -0.2%     
========================================
  Files          11      11             
  Lines         872     886     +14     
  Branches      131     133      +2     
========================================
+ Hits          691     701     +10     
- Misses        140     143      +3     
- Partials       41      42      +1     

Impacted Files	Coverage Δ
src/insight/metrics/__init__.py	100.0% <ø> (ø)
src/insight/metrics/metrics.py	90.5% <73.3%> (-1.4%)	:arrow_down:

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

92.0% Coverage
0.0% Duplication