Provide named export for clsx

[danikaze]

Fixes #43

[codecov-commenter]

Codecov Report

Merging #44 (7fccd49) into master (74cefa6) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master       #44   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines           22        22           
=========================================
  Hits            22        22           

Impacted Files	Coverage Δ
src/index.js	100.00% <ø> (ø)

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[Linus-Boehm]

Not a big issue, but this will make https://github.com/import-js/eslint-plugin-import/blob/main/docs/rules/no-named-as-default.md complain.