Install Node/NPM in docker dev environment

We are working on replacing SASS compilation (and later JS bundling)
with webpack, which will require Node and NPM.  This change adds these
tools to the Docker-based development environment so everything can
be built there.

Dockerfile

@@ -35,7 +35,13 @@ RUN apt-get update && \
             locales \
             python3-dbg gdb \
             sudo python3-dev python3-pip python3-virtualenv build-essential supervisor \
-	    debian-keyring debian-archive-keyring ca-certificates
+	    debian-keyring debian-archive-keyring ca-certificates curl gpg
+
+## Use deb.nodesource.com to fetch more modern versions of Node/NPM than Debian can provide
+RUN curl -fsSL https://deb.nodesource.com/gpgkey/nodesource-repo.gpg.key | gpg --dearmor -o /usr/share/keyrings/nodesource.gpg && \
+    echo 'deb [arch=amd64 signed-by=/usr/share/keyrings/nodesource.gpg] https://deb.nodesource.com/node_20.x nodistro main' > /etc/apt/sources.list.d/nodesource.list && \
+    apt-get update && \
+    apt-get install -y nodejs
 
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 ARG LOCALE=en_US.UTF-8