ci: add docker build workflow for waitlist website

Builds and pushes to cr.nym.sh on pushes to master
that touch apps/waitlist-website/.

Co-authored-by: Ona <no-reply@ona.com>

.github/workflows/build-waitlist-website.yml

@@ -0,0 +1,42 @@
+name: Build waitlist website
+
+on:
+  push:
+    branches: [master]
+    paths:
+      - apps/waitlist-website/**
+      - .github/workflows/build-waitlist-website.yml
+
+  workflow_dispatch:
+
+env:
+  REGISTRY: cr.nym.sh
+  IMAGE_NAME: waitlist-website
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Log in to container registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ secrets.REGISTRY_USERNAME }}
+          password: ${{ secrets.REGISTRY_PASSWORD }}
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: apps/waitlist-website
+          push: true
+          tags: |
+            ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:latest
+            ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.sha }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max