Add array_map_unique() helper

[caendesilva]

Adds a helper which is a wrapper for the array_map function. However, the returned array is filtered for duplicates and its keys are reset. The callback function also comes after the original array as I think that presents a more logical developer flow.

[codecov]

Codecov Report

Merging #175 (122a8fb) into master (4f60f63) will not change coverage.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##              master      #175   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
  Complexity       770       770           
===========================================
  Files            100       100           
  Lines           1993      1996    +3     
===========================================
+ Hits            1993      1996    +3     

Impacted Files	Coverage Δ
packages/framework/src/helpers.php	100.00% <100.00%> (ø)

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