fix: Fixing dependency issues that arise in the docker image. (#601)

The dockerfile didn't previously copy in the package-lock file which
means package dependency issues could occasionally arise. This is fixed
by simply copying in the package-lock file.

(cherry picked from commit ca62a87)

Author: mcottontensor

SignallingWebServer/Dockerfile

@@ -4,6 +4,7 @@ FROM node:lts
 WORKDIR /SignallingWebServer
 COPY NODE_VERSION ./NODE_VERSION
 COPY package.json ./package.json
+COPY package-lock.json ./package-lock.json
 COPY /Common ./Common
 COPY /Signalling ./Signalling
 COPY /SignallingWebServer ./SignallingWebServer