Add simple to string which print human readable string

[iamquang95]

No description provided.

[codecov-io]

Codecov Report

Merging #4 into master will increase coverage by 3.03%.
The diff coverage is 100%.

@@           Coverage Diff            @@
##           master     #4      +/-   ##
========================================
+ Coverage   96.96%   100%   +3.03%     
========================================
  Files           1      1              
  Lines          33     53      +20     
========================================
+ Hits           32     53      +21     
+ Misses          1      0       -1

Impacted Files	Coverage Δ
filesize.go	100% <100%> (+3.03%)	⬆️

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