feat: Add shell completions for Nushell and Elvish #244

Job	Run time
General Pull Request Checks / Run Cargo Deny (advisories)	41s
General Pull Request Checks / Run Cargo Deny (bans licenses sources)	46s
General Pull Request Checks / Run Cargo Udeps	2m 14s
General Pull Request Checks / Run Clippy	1m 4s
General Pull Request Checks / Run RustDoc	2m 11s
General Pull Request Checks / Run Rustfmt	12s
General Pull Request Checks / Run Cargo Tests	1m 50s
General Pull Request Checks / All tests passed	1s
Helm Chart Check	17s
Publish amd64 Image	13m 32s
Publish arm64 Image	15m 34s
Build and publish manifest list	54s
	39m 16s

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