add dumb init

Dockerfile

-FROM node:buster
+FROM node:buster-slim
 LABEL Author="Nanahira <nanahira@momobako.com>"
 
 RUN apt-get update \
@@ -6,7 +6,7 @@ RUN apt-get update \
     && wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | apt-key add - \
     && sh -c 'echo "deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google.list' \
     && apt-get update \
-    && apt-get install -y python3 build-essential google-chrome-stable fonts-ipafont-gothic fonts-wqy-microhei fonts-wqy-zenhei fonts-thai-tlwg fonts-kacst fonts-freefont-ttf libxss1 \
+    && apt-get install -y python3 build-essential google-chrome-stable fonts-ipafont-gothic fonts-wqy-microhei fonts-wqy-zenhei fonts-thai-tlwg fonts-kacst fonts-freefont-ttf libxss1 dumb-init \
       --no-install-recommends \
     && rm -rf /tmp/* /var/tmp/* /var/lib/apt/lists/*
 
@@ -17,4 +17,5 @@ RUN npm ci && \
 COPY . ./
 RUN npm run build
 
+ENTRYPOINT ["/usr/bin/dumb-init", "--"]
 CMD ["npm", "run", "start:prod"]