Add custom-elements.json for vscode

stencil.config.ts

@@ -31,6 +31,10 @@ export const config: Config = {
       type: 'docs-json',
       file: './dist/components.json'
     },
+    {
+      type: 'docs-vscode',
+      file: './dist/custom-elements.json'
+    },
     {
       type: 'www',
       serviceWorker: undefined // disable service workers