Generate normalized cache context relative paths

[mistic]

This PR enables the cache context relative paths generation to always use normalized posix paths instead of specific OS ones.

\CC @evilebottnawi

[alexander-akait]

Looks great, let's add couple tests

[mistic]

@evilebottnawi tests added

[mistic]

@evilebottnawi can we merge this?

[alexander-akait]

@mistic let's fix conflict and we can merge, also will be great fix CI before release new version

[codecov]

Codecov Report

Merging #54 into master will increase coverage by 0.35%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master      #54      +/-   ##
==========================================
+ Coverage   58.11%   58.47%   +0.35%     
==========================================
  Files           2        2              
  Lines         117      118       +1     
  Branches       17       17              
==========================================
+ Hits           68       69       +1     
  Misses         42       42              
  Partials        7        7

Impacted Files	Coverage Δ
src/index.js	58.97% <66.66%> (+0.35%)	⬆️

---

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[codecov]

Codecov Report

Merging #54 into master will increase coverage by 0.35%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master      #54      +/-   ##
==========================================
+ Coverage   58.11%   58.47%   +0.35%     
==========================================
  Files           2        2              
  Lines         117      118       +1     
  Branches       17       17              
==========================================
+ Hits           68       69       +1     
  Misses         42       42              
  Partials        7        7

Impacted Files	Coverage Δ
src/index.js	58.97% <66.66%> (+0.35%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 148b2a0...a45f3af. Read the comment docs.