Add the sponsor link (Buy Me a Coffee); 0.6.2

package.json declares sponsor.url, so the Extensions view and the
Marketplace page show a Sponsor button. The README mentions it after
the introduction and gets a Support section with the button.

package.json

@@ -2,9 +2,12 @@
   "name": "archify-vscode-ext",
   "displayName": "Archify Diagram Viewer",
   "description": "Archify diagrams in VS Code. Write diagrams as .archify files in YAML: they open as the interactive diagram, with live updates, validation, templates and completion. Also previews Archify's own JSON files (*.architecture.json, …) and opens rendered Archify HTML.",
-  "version": "0.6.1",
+  "version": "0.6.2",
   "publisher": "root-at-skic",
   "license": "MIT",
+  "sponsor": {
+    "url": "https://buymeacoffee.com/root.at.skic"
+  },
   "icon": "media/icon.png",
   "galleryBanner": {
     "color": "#0f172a",