clean up & simplify structure w/ separate build workflows

Independent NGINX & PHP-FPM build workflows & directory structure for
cleaner and simpler workflow logic.

nginx/Dockerfile

@@ -0,0 +1,10 @@
+FROM nginx:alpine-slim
+
+# Copy nginx config from repo
+COPY --chown=root:root nginx/nginx.conf /etc/nginx/conf.d/default.conf
+
+RUN mkdir -p /var/www/html /var/log/nginx && chown -R nginx:nginx /var/www/html /var/log/nginx
+
+EXPOSE 80
+
+CMD ["nginx", "-g", "daemon off;"]