fix: add support for multi-line import extension normalization

[alexgrozav]

Fixes #45 and unjs/unbuild#83.

The change essentially does the following:

• One-line imports are handled as they were before
• Multi-line imports are handled only if brackets are present, allowing full control over the multi-line capture group, so that we don't mistakenly capture functions and objects that use brackets.

The simplest solution of using [\s\S] instead of .* will spill over to export function() {} and export {};, therefore it's not feasible.

[danielroe]

This looks good to me - thanks!

[codecov]

Codecov Report

Merging #120 (0fa3d1e) into main (01f72a5) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #120   +/-   ##
=======================================
  Coverage   96.09%   96.09%           
=======================================
  Files           8        8           
  Lines         487      487           
  Branches       98       98           
=======================================
  Hits          468      468           
  Misses         19       19           

Impacted Files	Coverage Δ
src/make.ts	89.70% <100.00%> (ø)

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[pi0]

Thanks for the fix and sorry for delay. Later, we might change this to mlly utils for more stable impl.