Fix: Update to node:18.16.1 in Dockerfile

The original OHIF repository added this update, due to a deprecancy issue with node, see [here](https://github.com/OHIF/Viewers/blob/master/Dockerfile#L24).

I added the same fix to my HF Space deployment and it works great, see [here](https://github.com/andreped/ohif4hf/pull/11/files), so I believe it should work for this Space as well.

Dockerfile

@@ -1,4 +1,4 @@
-FROM node:16.15.0-slim as json-copier
+FROM node:18.16.1-slim as json-copier
 
 RUN mkdir /usr/src/app
 WORKDIR /usr/src/app
@@ -18,7 +18,7 @@ RUN git clone --recursive https://github.com/OHIF/Viewers.git .
 #RUN find platform \! -name "package.json" -mindepth 2 -maxdepth 2 -print | xargs rm -rf
 
 # Copy Files
-FROM node:16.15.0-slim as builder
+FROM node:18.16.1-slim as builder
 RUN apt-get update && apt-get install -y build-essential python3
 RUN mkdir /usr/src/app
 WORKDIR /usr/src/app