fix: add Context trait and correct with_context usage

src/digest_engine.rs

@@ -1,4 +1,4 @@
-use anyhow::{anyhow, Result};
+use anyhow::{anyhow, Context, Result};
 use std::io;
 
 use lazy_static::lazy_static;

src/digest_engine/program.rs

@@ -52,7 +52,7 @@ impl DigestEngine for DigestEngineProgram {
             .stdin(Stdio::piped())
             .stdout(Stdio::piped())
             .spawn()
-            .context(anyhow!(
+            .with_context(anyhow!(
                 "Problem spawning child process: {:?} {:?}",
                 program,
                 args