Add napari-hub preview workflow

Author: dstansby

.github/workflows/napari_hub_preview.yml

@@ -0,0 +1,21 @@
+name: napari hub Preview Page # we use this name to find your preview page artifact, so don't change it!
+# For more info on this action, see https://github.com/chanzuckerberg/napari-hub-preview-action/blob/main/action.yml
+
+on:
+  pull_request:
+    branches:
+      - '**'
+
+jobs:
+  preview-page:
+    name: Preview Page Deploy
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v2
+
+      - name: napari hub Preview Page Builder
+        uses: chanzuckerberg/napari-hub-preview-action@v0.1.5
+        with:
+          hub-ref: main