use .nvmrc in the docker file

Author: millotp

DOCKER_README.MD

@@ -8,7 +8,7 @@ Install [Docker Desktop](https://docs.docker.com/get-docker/).
 ## Build the image
 
 ```bash
-docker build -t algolia-js .
+docker build -t algolia-js --build-arg NODE_IMAGE=node:$(cat .nvmrc)-alpine .
 ```
 
 ## Run the image

Dockerfile

@@ -1,5 +1,7 @@
 # Dockerfile
-FROM node:12.16.2-alpine
+ARG NODE_IMAGE=node:12.16.0-alpine
+
+FROM $NODE_IMAGE
 
 # Install the dependencies in the parent folder so they don't get overriden by the bind mount
 WORKDIR /