Add pgsql driver to docker image

Dockerfile

 FROM php:apache
 
 RUN docker-php-ext-install pdo pdo_mysql
-    
+
+RUN apt-get update; \
+    apt-get install -y libpq5 libpq-dev; \
+    docker-php-ext-install pdo pdo_pgsql; \
+    apt-get autoremove --purge -y libpq-dev; \
+    apt-get clean ; \
+    rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* /usr/share/doc/*    
+
 RUN a2enmod rewrite
 
 COPY api.php /var/www/html/api.php