fix(index): handle chunks provided as a {Set}

[ooflorent]

This PR contains a:

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

Motivation / Use-Case

In webpack@5, chunks is a Set and thus should be converted to an array.

Breaking Changes

n/a

Additional Info

This change makes the plugin compatible with webpack 4 and 5.

[codecov]

Codecov Report

Merging #365 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #365   +/-   ##
=======================================
  Coverage   97.69%   97.69%           
=======================================
  Files           5        5           
  Lines         260      260           
  Branches      102      102           
=======================================
  Hits          254      254           
  Misses          6        6

Impacted Files	Coverage Δ
src/index.js	96.4% <100%> (ø)	⬆️

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