build: update the recommended Dockerfile for VSCode remote development (#41396)

This commit updates the recommended `Dockerfile` for VSCode remote
development to take into account recent changes in our dev workflow
(updated Node.js version, vendored yarn, modified CircleCI config).

It also adds a note in the CircleCI config to keep the recommended
`Dockerfile` up-to-date with the Node.js version used on CI.

PR Close #41396

.devcontainer/recommended-Dockerfile

@@ -1,8 +1,8 @@
 # Image metadata and config.
-# Ideally, the image version should be what we use on CI.
-# See `executors > browsers-executor` in `.circleci/config.yml`.
-FROM circleci/node:10-browsers  
-                                
+# Ideally, the Node.js version should match what we use on CI.
+# See `executors > default-executor` in `.circleci/config.yml`.
+FROM circleci/node:12-browsers
+
 
 LABEL name="Angular dev environment" \
       description="This image can be used to create a dev environment for building Angular." \
@@ -16,13 +16,9 @@ EXPOSE 4000 4200 4433 5000 8080 9876
 USER root
 
 
-# Configure `Node.js`/`npm` and install utilities.
+# Configure `Node.js`/`npm`.
 RUN npm config --global set user root
 
-# Ideally, the version should be what we use on CI.
-# See `commands > overwrite_yarn` in `.circleci/config.yml`.
-RUN npm install --global yarn@latest
-
 
 # Go! (And keep going.)
 CMD ["tail", "--follow", "/dev/null"]