feat: Add shell completions for Nushell and Elvish #243

Job	Run time
General Pull Request Checks / Run Cargo Deny (advisories)	41s
General Pull Request Checks / Run Rustfmt	13s
General Pull Request Checks / Run Cargo Deny (bans licenses sources)	41s
General Pull Request Checks / Run Clippy	2m 49s
General Pull Request Checks / Run Cargo Udeps	8m 3s
General Pull Request Checks / Run RustDoc	3m 46s
General Pull Request Checks / Run Cargo Tests	3m 31s
General Pull Request Checks / All tests passed	1s
Helm Chart Check	16s
Publish amd64 Image	14m 39s
Publish arm64 Image	17m 16s
Build and publish manifest list	53s
	52m 49s

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