feat(cli): print completion scripts and the man page to stdout

`completions install` writes into a home directory, which a package
build does not have. `completions print <shell>` and `man` give it the
files to put under /usr/share instead.

soulseek-rs/Cargo.toml

@@ -30,6 +30,7 @@ soulseek-rs-lib = { version = "19.0.0", path = "../soulseek-rs-lib" }
 
 clap = { version = "4.6.2", features = ["derive", "color", "wrap_help", "env"] }
 clap_complete = "4.6.7"
+clap_mangen = "0.3.3"
 ratatui = "0.30.2"
 unicode-width = "0.2"
 color-eyre = "0.6.5"