docs: replace spread and euler demo cards with elk

Agent-Logs-Url: https://github.com/cytoscape/cytoscape.js/sessions/9e7d676a-b461-4fae-9e55-535b0fcd770f

Co-authored-by: maxkfranz <989043+maxkfranz@users.noreply.github.com>

Author: Copilot

documentation/docmaker.json

@@ -63,8 +63,7 @@
         { "name": "fCoSE layout (constraint)", "id": "fcose-layout-constraint", "github": "iVis-at-Bilkent/cytoscape.js-fcose", "viewUrl": "https://ivis-at-bilkent.github.io/cytoscape.js-fcose/demo/demo-constraint.html" },
         { "name": "Cola layout", "id": "cola-layout", "github": "cytoscape/cytoscape.js-cola" },
         { "name": "Cola layout (compound)", "id": "cola-layout-compound", "github": "cytoscape/cytoscape.js-cola", "viewUrl": "https://cytoscape.github.io/cytoscape.js-cola/demo-compound.html" },
-        { "name": "Euler layout", "id": "euler-layout", "github": "cytoscape/cytoscape.js-euler" },
-        { "name": "Spread layout", "id": "spread-layout", "github": "cytoscape/cytoscape.js-spread" },
+        { "name": "ELK layout", "id": "elk-layout", "github": "cytoscape/cytoscape.js-elk", "viewUrl": "https://cytoscape.github.io/cytoscape.js-elk/?demo=layered" },
         { "name": "Dagre layout", "id": "dagre-layout", "github": "cytoscape/cytoscape.js-dagre" },
         { "name": "Klay layout", "id": "klay-layout", "github": "cytoscape/cytoscape.js-klay" },
         { "name": "Breadthfirst layout & images", "id": "images-breadthfirst-layout" },