Issue #000 fix: changing nginx image from alpine to debian

as lua support is incorrect in nginx-1.16-alpine

images/proxy/Dockerfile

-FROM nginx:1.13.12-alpine
+FROM nginx:1.16
 
-COPY prometheus.lua /etc/nginx/lua_modules/
-COPY nginx.conf /etc/nginx/nginx.conf
-RUN apk add --no-cache nginx-mod-http-lua \
+RUN apt update && apt install nginx-extras -y \
+    && apt autoremove -y \
     && rm -rf /etc/nginx/conf.d \
     && rm -rf /usr/share/nginx/html
+COPY prometheus.lua /etc/nginx/lua_modules/
+COPY nginx.conf /etc/nginx/nginx.conf