Add build script, generate man page at build-time

build.rs

@@ -0,0 +1,20 @@
+use clap::CommandFactory;
+use clap_mangen::Man;
+use std::env;
+use std::fs;
+use std::io;
+use std::path::PathBuf;
+
+mod cli {
+    include!("src/cli.rs");
+}
+
+fn main() -> std::io::Result<()> {
+    let out_dir = PathBuf::from(env::var_os("OUT_DIR").ok_or(io::ErrorKind::NotFound)?);
+    let cmd = cli::Cli::command();
+    let man = Man::new(cmd);
+    let mut buffer: Vec<u8> = Default::default();
+    man.render(&mut buffer)?;
+
+    fs::write(out_dir.join("asciinema.1"), buffer)
+}