fix: add missing imports for sha2, Command, and Stdio

src/compression_engine/program.rs

@@ -5,6 +5,7 @@ use std::fs;
 use std::fs::File;
 use std::io::{Read, Write};
 use std::os::unix::fs::PermissionsExt;
+use std::process::{Command, Stdio};
 use std::path::PathBuf;
 
 use crate::compression_engine::CompressionEngine;

src/digest_engine/sha2.rs

@@ -1,5 +1,6 @@
 use std::io;
 use sha2::{Digest, Sha256};
+use sha2::{Digest, Sha256};
 
 #[derive(Debug, Eq, PartialEq, Clone, Default)]
 pub struct DigestEngineSha256 {