fix: add missing std::io::Write import for md5::Context write method

Co-authored-by: aider (openai/andrew/openrouter/deepseek/deepseek-chat-v3.1) <aider@aider.chat>

src/meta_plugin/digest.rs

@@ -2,6 +2,7 @@ use sha2::{Digest, Sha256, Sha512};
 use md5;
 use crate::meta_plugin::MetaPlugin;
 use std::fmt;
+use std::io::Write;
 
 #[derive(Clone)]
 enum Hasher {