Update Dockerfile

Add non-root user for ffmpeg installation

laravel-horizon/Dockerfile

@@ -26,6 +26,15 @@ RUN apk --update add wget \
 RUN docker-php-ext-install mysqli mbstring pdo pdo_mysql tokenizer xml pcntl
 RUN pecl channel-update pecl.php.net && pecl install memcached mcrypt-1.0.1 mongodb && docker-php-ext-enable memcached mongodb
 
+# Add a non-root user to help install ffmpeg:
+ARG PUID=1000
+ENV PUID ${PUID}
+ARG PGID=1000
+ENV PGID ${PGID}
+
+RUN addgroup -g ${PGID} laradock && \
+    adduser -D -G laradock -u ${PUID} laradock
+
 #Install BCMath package:
 ARG INSTALL_BCMATH=false
 RUN if [ ${INSTALL_BCMATH} = true ]; then \