Extract euph config into submodule

cove-config/src/doc.rs

@@ -1,6 +1,10 @@
+//! Auto-generate markdown documentation.
+
 use std::collections::HashMap;
 use std::path::PathBuf;
 
+pub use cove_macro::Document;
+
 #[derive(Clone, Default)]
 pub struct ValueInfo {
     pub required: Option<bool>,