Speed up docker build (#17659)

Co-authored-by: Chiedo John <2156688+chiedo@users.noreply.github.com>

Author: heiskr

Dockerfile

@@ -1,35 +1,20 @@
 # This Dockerfile can be used for docker-based deployments to platforms
 # like Now or Moda, but it is currently _not_ used by our Heroku deployments
-# It uses three multi-stage builds: `installation`, `bundles`, and the main build.
+# It uses two multi-stage builds: `install` and the main build to keep the image size down.
 
 # --------------------------------------------------------------------------------
-# INSTALLATION IMAGE
-# A temporary image that installs production-only dependencies
+# INSTALL IMAGE
+# A temporary image that installs production-only dependencies and builds the production-ready front-end bundles.
 
-FROM node:14-alpine as installation
+FROM node:14-alpine as install
 RUN apk add --no-cache python make g++
 ENV NODE_ENV production
 WORKDIR /usr/src/docs
 COPY package*.json ./
-
-# Install the project's dependencies
-RUN npm ci --production
-
-# --------------------------------------------------------------------------------
-# BUNDLE IMAGE
-# A temporary image that installs dependencies and builds the production-ready front-end bundles.
-
-FROM node:14-alpine as bundles
-RUN apk add --no-cache python make g++
-ENV NODE_ENV production
-WORKDIR /usr/src/docs
-# Install the files used to create the bundles
-COPY package*.json ./
 COPY javascripts ./javascripts
 COPY stylesheets ./stylesheets
 COPY lib ./lib
 COPY webpack.config.js ./webpack.config.js
-# Install the project's dependencies and build the bundles
 RUN npm ci --production
 RUN npm run build
 
@@ -48,10 +33,10 @@ RUN chown node:node /usr/src/docs -R
 USER node
 
 # Copy our dependencies
-COPY --chown=node:node --from=installation /usr/src/docs/node_modules /usr/src/docs/node_modules
+COPY --chown=node:node --from=install /usr/src/docs/node_modules /usr/src/docs/node_modules
 
 # Copy our front-end code
-COPY --chown=node:node --from=bundles /usr/src/docs/dist /usr/src/docs/dist
+COPY --chown=node:node --from=install /usr/src/docs/dist /usr/src/docs/dist
 
 # We should always be running in production mode
 ENV NODE_ENV production