Add some imports that the configuration library needs

config/src/lib.rs

@@ -95,6 +95,9 @@ macro_rules! define_config {
 mod test {
     use super::*;
     use cool_asserts::assert_matches;
+    use serde::{Deserialize, Serialize};
+    use std::collections::HashMap;
+    use std::path::PathBuf;
 
     define_config! {
         DatabasePath(DatabasePath),