Switch to time crate, add file sizes (#329)

* Switch to time crate, add file sizes

* Update deps, adjust pack format

* Run formatter, fix clippy

src/routes/maven.rs

@@ -108,7 +108,7 @@ pub async fn maven_metadata(
                     .map(|x| x.version_number.clone())
                     .collect::<Vec<_>>(),
             },
-            last_updated: data.inner.updated.format("%Y%m%d%H%M%S").to_string(),
+            last_updated: data.inner.updated.format("%Y%m%d%H%M%S"),
         },
     };