docs: Add new completions, simplify install instructions #52

Job	Run time
General Pull Request Checks / Run Cargo Deny (advisories)	38s
General Pull Request Checks / Run Clippy	1m 14s
General Pull Request Checks / Run Cargo Deny (bans licenses sources)	41s
General Pull Request Checks / Run RustDoc	1m 55s
General Pull Request Checks / Run Rustfmt	12s
General Pull Request Checks / Run Cargo Tests	1m 17s
General Pull Request Checks / Run Cargo Udeps	1m 53s
General Pull Request Checks / All tests passed	1s
	7m 51s

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