added WithReferenceCount option

[Code-Hex]

for #34

[codecov]

Codecov Report

Merging #38 (9c36caf) into main (8c94293) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main       #38   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            9        10    +1     
  Lines          521       533   +12     
=========================================
+ Hits           521       533   +12     

Impacted Files	Coverage Δ
policy/lfu/lfu.go	100.00% <ø> (ø)
cache.go	100.00% <100.00%> (ø)
policy/clock/clock.go	100.00% <100.00%> (ø)
policy/internal/policyutil/reference_count.go	100.00% <100.00%> (ø)
policy/lfu/priotiry_queue.go	100.00% <100.00%> (ø)

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