build: fully qualify images in Dockerfile

This avoids errors building the image with podman.

https://www.redhat.com/sysadmin/container-image-short-names

Dockerfile

@@ -1,10 +1,10 @@
-FROM node:16 AS build
+FROM docker.io/library/node:16 AS build
 
 ADD . /usr/src/app
 WORKDIR /usr/src/app
 RUN yarn install && yarn build
 
-FROM nginx:stable
+FROM docker.io/library/nginx:stable
 
 RUN chmod g+rwx /var/cache/nginx /var/run /var/log/nginx
 COPY --from=build /usr/src/app/dist /usr/share/nginx/html