Add php extension fileinfo

Dockerfile

@@ -73,7 +73,7 @@ RUN echo 'hosts: files dns' > /etc/nsswitch.conf && \
     echo "http://dl-cdn.alpinelinux.org/alpine/v${ALPINE_VERSION}/community" >> /etc/apk/repositories && \
     apk update && \
     apk add --no-cache \
-        php7 php7-phar php7-json php7-dom php7-gd php7-mbstring php7-openssl \
+        php7 php7-phar php7-json php7-dom php7-fileinfo php7-gd php7-mbstring php7-openssl \
         php7-pdo php7-curl php7-xml php7-zip php7-session php7-ctype php7-iconv \
         php7-bcmath && \
     if [ "${PHP_VERSION}" = "7.0" ]; then \