feat: allow the additionalData to be async

[alexander-akait]

This PR contains a:

• bugfix
• new feature
• code refactor
• test update
• typo fix
• metadata update

Motivation / Use-Case

async additionalData + improvements

Breaking Changes

No

Additional Info

No

[codecov]

Codecov Report

Merging #902 (3f08237) into master (e4afcd7) will increase coverage by 0.13%.
The diff coverage is 87.93%.

@@            Coverage Diff             @@
##           master     #902      +/-   ##
==========================================
+ Coverage   96.01%   96.15%   +0.13%     
==========================================
  Files           4        4              
  Lines         226      234       +8     
  Branches       72       73       +1     
==========================================
+ Hits          217      225       +8     
  Misses          8        8              
  Partials        1        1              

Impacted Files	Coverage Δ
src/utils.js	95.33% <85.10%> (+0.12%)	⬆️
src/SassError.js	100.00% <100.00%> (ø)
src/cjs.js	100.00% <100.00%> (ø)
src/index.js	100.00% <100.00%> (ø)

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