Split line installing packages in Dockerfile

With one package in line and in alphabetic order, it's easier to see
which packages we're installing.

We're also applying the same formatting (taking from the Docker
documentation [1]) to other lines running multiple instructions.

[1] https://docs.docker.com/develop/develop-images/dockerfile_best-practices/#run

Dockerfile

@@ -3,7 +3,23 @@ FROM ruby:2.7.4-buster
 ENV DEBIAN_FRONTEND noninteractive
 
 # Install essential Linux packages
-RUN apt-get update -qq && apt-get install -y build-essential libpq-dev postgresql-client nodejs imagemagick sudo libxss1 libappindicator1 libindicator7 unzip memcached cmake pkg-config shared-mime-info
+RUN apt-get update -qq \
+ && apt-get install -y \
+    build-essential \
+    cmake \
+    imagemagick \
+    libappindicator1 \
+    libindicator7 \
+    libpq-dev \
+    libxss1 \
+    memcached \
+    nodejs \
+    pkg-config \
+    postgresql-client \
+    shared-mime-info \
+    sudo \
+    unzip
+
 # Install Chromium for E2E integration tests
 RUN apt-get update -qq && apt-get install -y chromium