Updated dockerfile to support Windows builds

backend/Dockerfile

@@ -16,10 +16,14 @@ RUN apk add --no-cache \
 # switch to default user to not chown node_modules on startup
 USER $USER
 WORKDIR /app
-
 COPY --chown=$UID:$GID [ "package.json", "package-lock.json", "/app/" ]
+
+# run npm install as root, required for Windows hosts
+USER root
 RUN npm install
 
+RUN chown -R $UID:$GID ./
+
 COPY --chown=$UID:$GID [ "./", "/app/" ]
 
 EXPOSE 17442