Export internal type to fix the documentation

[mangalaman93]

No description provided.

[codecov]

Codecov Report

Merging #19 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master      #19   +/-   ##
=======================================
  Coverage   87.69%   87.69%           
=======================================
  Files           3        3           
  Lines          65       65           
=======================================
  Hits           57       57           
  Misses          4        4           
  Partials        4        4

Impacted Files	Coverage Δ
mmap_data.go	94.28% <100%> (ø)	⬆️
mmap_page.go	66.66% <100%> (ø)	⬆️
mmap.go	100% <100%> (ø)	⬆️

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