[pull] l2d from carpentries:main (#92)

* Upgrade upload-artifact to v4

* Update checkout to v4

* Translate new dark theme toggle string to French

* Compile FR translations

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Co-authored-by: Hugo Gruson <[email protected]>
Co-authored-by: Erin Becker <[email protected]>
Co-authored-by: Robert Davey <[email protected]>