ci: trying to add build docker image

.github/Dockerfile

@@ -0,0 +1,16 @@
+ARG PHP_VERSION=8.2.11
+ARG COMPOSER_VERSION=2.6.5
+
+FROM php:${PHP_VERSION}-cli-alpine
+
+COPY --from=composer:${COMPOSER_VERSION} /usr/bin/composer /usr/bin/composer
+
+WORKDIR /app
+
+COPY composer.json composer.json
+RUN composer update --no-dev
+
+COPY merger merger
+COPY src src
+
+ENTRYPOINT ["/app/merger"]