feat: compile time completion generation

Removed `completion` command in favor of compile time completion
generation. This tool will only be build from source for the foreseeable
future so this makes sense for now.

Cargo.toml

@@ -7,6 +7,7 @@ edition = "2021"
 license = "MIT"
 authors = ["Matej Janežič <janezic.mj@gmail.com>"]
 repository = "https://github.com/janezicmatej/ahab.git"
+build = "build.rs"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
@@ -15,3 +16,7 @@ clap = { version = "4.3.0", features = ["derive"] }
 clap_complete = "4.3.0"
 anyhow = "1.0.71"
 dotenvy = "0.15.7"
+
+[build-dependencies]
+clap = { version = "4.3.0", features = ["derive"] }
+clap_complete = "4.3.0"