Add Docker

tools/docker/composer/Dockerfile

@@ -0,0 +1,26 @@
+FROM php:7.4-cli
+
+COPY tools/docker/composer/composer-installer.sh /usr/local/bin/composer-installer
+
+RUN apt-get -yqq update \
+  && apt-get -yqq install --no-install-recommends \
+    git \
+    libpng-dev \
+    unzip \
+    wget \
+    zip \
+  && apt-get autoremove -y --purge \
+  && rm -fr /var/lib/apt/lists/* \
+  && chmod +x /usr/local/bin/composer-installer \
+  && composer-installer \
+  && mv composer.phar /usr/local/bin/composer \
+  && chmod +x /usr/local/bin/composer \
+  && composer --version
+
+RUN docker-php-ext-install gd
+
+COPY . /app
+
+WORKDIR /app
+
+ENTRYPOINT [ "/usr/local/bin/composer" ]

tools/docker/composer/composer-installer.sh

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+#!/bin/sh
+
+EXPECTED_CHECKSUM="$(wget -q -O - https://composer.github.io/installer.sig)"
+php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"
+ACTUAL_CHECKSUM="$(php -r "echo hash_file('sha384', 'composer-setup.php');")"
+
+if [ "$EXPECTED_CHECKSUM" != "$ACTUAL_CHECKSUM" ]
+then
+    >&2 echo 'ERROR: Invalid installer checksum'
+    rm composer-setup.php
+    exit 1
+fi
+
+php composer-setup.php --quiet
+RESULT=$?
+rm composer-setup.php
+exit $RESULT