Add LNK metric

[DragaDoncila]

Proposed Change

Add LNK metric giving 0 weight to node errors. Closes #187.

Types of Changes

• New feature or enhancement
• Documentation update

Which topics does your change affect? Delete those that do not apply.

• Metrics

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• I have read the developer/contributing docs.
• I have added tests that prove that my feature works in various situations or tests the bugfix (if appropriate).
• I have checked that I maintained or improved code coverage.
• I have checked the benchmarking action to verify that my changes did not adversely affect performance.
• I have written docstrings and checked that they render correctly in the Read The Docs build (created after the PR is opened).
• I have updated the general documentation including Metric descriptions and example notebooks if necessary.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.20%. Comparing base (31be450) to head (8759618).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #205      +/-   ##
==========================================
+ Coverage   95.00%   95.20%   +0.20%     
==========================================
  Files          18       18              
  Lines         921      939      +18     
==========================================
+ Hits          875      894      +19     
+ Misses         46       45       -1     

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[DragaDoncila]

@cmalinmayor @msschwartz21 this ended up a pretty small change, but feedback welcome! I added some more tests but let me know if there's anything you think is missing