dockerfile: node:12-slim => node:14-slim

dockerfile

@@ -1,5 +1,5 @@
 # build environment
-FROM node:12-slim as builder
+FROM node:14-slim as builder
 WORKDIR /app
 
 COPY .npmrc .npmrc 
@@ -11,7 +11,7 @@ COPY . ./
 RUN npm run build
 
 # production environment
-FROM node:12-slim
+FROM node:14-slim
 RUN printf '\n\n- Copy application files\n'
 
 ARG APP_SUBFOLDER=network-resurrector