refactor: set the 'Dockerfiles' to use 'Alpine' images as the base

.docker/php/php.dockerfile

@@ -0,0 +1 @@
+FROM php:7.4-fpm-alpine

.docker/server/nginx.dockerfile

@@ -0,0 +1 @@
+FROM nginx:stable-alpine

Dockerfile

@@ -1,4 +1,4 @@
-FROM docker:20.10
+FROM docker:20.10-cli
 WORKDIR "/home/librex"
 
 # Docker metadata contains information about the maintainer, such as the name, repository, and support email