init app of test arena

asf-cloud-server/testarena/frontend/Dockerfile

@@ -0,0 +1,10 @@
+FROM node:18-alpine as build
+WORKDIR /app
+COPY package*.json ./
+RUN npm install
+COPY . .
+RUN npm run build
+
+FROM caddy:2-alpine
+COPY --from=build /app/dist /srv
+COPY Caddyfile /etc/caddy/Caddyfile