fix readme

README.md

@@ -70,7 +70,7 @@ data-view | When set, turns the web component into a viewer that displays the gi
 data-collapse | When set, `sh:group`s and properties with `sh:node` and `sh:maxCount` != 1 are displayed in a collapsible accordion-like widget to reduce visual complexity of the form. The collapsible element is initially shown closed, except when this attribute's value is `"open"`
 data-submit-button | [Ignored when `data-view` attribute is set] Whether to add a submit button to the form. The value of this attribute is used as the button label. `submit` events get emitted only when the form data validates
 data-generate-node-shape-reference | When generating the RDF data graph, <shacl-form> can create a triple that references the root `sh:NodeShape` of the data. Suggested values for this attribute are `http://www.w3.org/1999/02/22-rdf-syntax-ns#type` or `http://purl.org/dc/terms/conformsTo`. Default is empty, so that no such triple is created
-show-node-ids | When this attribute is set, shacl node shapes will have their subject id shown in the form
+data-show-node-ids | When this attribute is set, shacl node shapes will have their subject id shown in the form
 
 ### Element functions