Update chat-linker build instruction

Author: ForNeVeR

omnissiah/chat-linker/Dockerfile

@@ -1,8 +1,8 @@
 FROM node:8.7.0-alpine
 RUN apk update && apk add git
-RUN git clone https://github.com/jt3k/chat-linker.git /usr/app/src && cd /usr/app/src && git checkout 4aab67aa6a59368896d427f14060c59484ff0a37
-RUN cd /usr/app/src && npm install # TODO: Not stable enough; migrate to yarn
-COPY app-config.json /usr/app/src/app-config.json
-WORKDIR /usr/app/src
+RUN git clone https://github.com/jt3k/chat-linker.git /usr/app && cd /usr/app && git checkout 4aab67aa6a59368896d427f14060c59484ff0a37
+RUN cd /usr/app && npm install && npm run build # TODO: Not stable enough; migrate to yarn
+COPY app-config.json /usr/app/app-config.json
+WORKDIR /usr/app
 ENV NODE_ENV prod
-CMD ["node", "app.js"]
+CMD ["node", "dist/app.js"]