build: run tests in docker container during build

Reduces the risk of an updated Docker image breaking things unnoticed

Dockerfile

@@ -5,6 +5,7 @@ COPY package.json package-lock.json ./
 RUN npm clean-install
 COPY . ./
 RUN npm run build
+RUN npm run test
 
 FROM node:18.13.0-alpine as production
 RUN mkdir /peer-server