feat: Add MapEntries function

[skimhugo]

Add a method to transform map[k]v to a new map[s]r according to a given transformer to all entries.

[codecov-commenter]

Codecov Report

Base: 98.45% // Head: 90.34% // Decreases project coverage by -8.10% ⚠️

Coverage data is based on head (4aad748) compared to base (f44773e).
Patch coverage: 100.00% of modified lines in pull request are covered.

❗ Current head 4aad748 differs from pull request most recent head 09e62a3. Consider uploading reports for the commit 09e62a3 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #216      +/-   ##
==========================================
- Coverage   98.45%   90.34%   -8.11%     
==========================================
  Files          15       15              
  Lines        1812     1658     -154     
==========================================
- Hits         1784     1498     -286     
- Misses         26      157     +131     
- Partials        2        3       +1     

Flag	Coverage Δ
unittests	90.34% <100.00%> (-8.11%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
map.go	96.72% <100.00%> (+0.26%)	⬆️
tuples.go	63.37% <0.00%> (-36.63%)	⬇️
errors.go	92.37% <0.00%> (-6.16%)	⬇️
channel.go	87.64% <0.00%> (-4.78%)	⬇️
test.go	72.72% <0.00%> (-4.20%)	⬇️
slice.go	97.56% <0.00%> (-0.12%)	⬇️
math.go	100.00% <0.00%> (ø)
retry.go	100.00% <0.00%> (ø)
string.go	100.00% <0.00%> (ø)
... and 1 more

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[samber]

Hi @skimhugo and thanks for this first contribution.

This one is much appreciated! Let's merge.