fix(docker): compatibility updates due to upstream image update

Dockerfile

@@ -1,6 +1,8 @@
 FROM richarvey/nginx-php-fpm
 
-COPY ./poweradmin-2.1.7 /usr/share/nginx/html
-COPY ./config.inc.php /usr/share/nginx/html/inc/config.inc.php
+RUN apk add --no-cache php5-gettext
+
+COPY ./poweradmin-2.1.7 /var/www/html
+COPY ./config.inc.php /var/www/html/inc/config.inc.php
 
 ENV TEMPLATE_NGINX_HTML=0