Update README.md

Author: dachafra

README.md

@@ -7,6 +7,23 @@ The FNML specification, SHACL shapes, test-cases, and ontology.
 - SHACL shapes: http://w3id.org/rml/fnml/shapes
 - Test-cases: [test-cases](./test-cases)
 
+## Specification
+
+The specification webpage is generated from directory [/spec](spec).
+
+It is accessible using URL https://w3id.org/rml/fnml/spec.
+
+#### Edition quickstart
+
+- cd to [/spec](spec)
+- Edit sections/index.html
+- Make sure all your local assets are in the `resources` folder, and the links in your `index.html` file are relative (important because the publishing script creates multiple nested paths)
+- Run a HTTP server in this directory: `python3 -m http.server`
+- Open `index.html` with a browser as http://localhost:8000/index.html
+- Save as snapshot to `rendered.html` [using the respec functionality](https://respec.org/docs/#using-browser) (button ReSpec/Export/HTML) and copy it to this same folder
+
+URL https://w3id.org/rml/fnml/spec must redirect to the `/spec/docs`(docs) folder.
+
 ## License
 
 RML-FNML (c) by W3C Community Group on Knowledge Graph Construction