Explicitly using desired versions; added nano editor into dockerfile (less logs)

Dockerfile

@@ -4,11 +4,12 @@ WORKDIR /var/www
 
 # Installing needed packages
 RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
-    mysql-server \
+    mysql-server-5.7 \
+    nano \
     nginx \
-    php-fpm \
-    php-mysql \
-    php-cli \
+    php7.2-fpm \
+    php7.2-mysql \
+    php7.2-cli \
     && rm -rf /var/lib/apt/lists/* \
     && rm -rf /var/www/html \
     && rm /etc/nginx/sites-enabled/default