docs: update with new directory structure

Author: mankins

readme.md

@@ -8,5 +8,9 @@ The process of creating a signed UNL is manual and intentionally non-automated.
 
 To suggest an update to this list, make a Pull Request. If approved, the next build of the UNL will include these changes.
 
-- Only changes to `unl/unl-raw.yaml` are required in your Pull Request.
+- Only changes to `source/unl-raw.yaml` are required in your Pull Request.
+
+## Historical Record
+
+The `record` directory contains a historical record of the `unl.json` files, postfixed with `-YYYYMMDDNN` where `NN` is a 2-digit sequence number for the day.