config: add async tasks and polling infrastructure

jay-config/src/_private/string_error.rs

@@ -0,0 +1,15 @@
+use std::{
+    error::Error,
+    fmt::{Display, Formatter},
+};
+
+#[derive(Debug)]
+pub struct StringError(pub String);
+
+impl Display for StringError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        f.write_str(&self.0)
+    }
+}
+
+impl Error for StringError {}