test: e2e test for hamt-sharded directory content

[SgtPooki]

Title

test: e2e test for hamt-sharded directory content

Description

adds "Opening UnixFS file from HAMT-sharded directory" test from #134

Notes & open questions

N/A

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation if necessary (this includes comments as well)
• I have added tests that prove my fix is effective or that my feature works

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (4304333) to head (cf44e20).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #157   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines           35        35           
  Branches         5         5           
=========================================
  Hits            35        35           

Flag	Coverage Δ
node	100.00% <ø> (ø)

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