Add dumb-init to avoid zombie processes

dockerfile

@@ -12,7 +12,7 @@ RUN apt update && \
 COPY . .
 RUN npm install --legacy-peer-deps && npm run build && npm prune --production
 
-FROM node:14-bullseye-slim AS release
+FROM node:14-buster-slim AS release
 WORKDIR /app
 
 # Install Apprise,
@@ -21,7 +21,8 @@ WORKDIR /app
 RUN apt update && \
     apt --yes install python3 python3-pip python3-cryptography python3-six python3-yaml python3-click python3-markdown python3-requests python3-requests-oauthlib \
         sqlite3 \
-                iputils-ping && \
+        iputils-ping \
+        dumb-init && \
     pip3 --no-cache-dir install apprise && \
     rm -rf /var/lib/apt/lists/*
 
@@ -31,7 +32,7 @@ COPY --from=build /app /app
 EXPOSE 3001
 VOLUME ["/app/data"]
 HEALTHCHECK --interval=60s --timeout=30s --start-period=180s --retries=5 CMD node extra/healthcheck.js
-CMD ["node", "server/server.js"]
+CMD ["/usr/bin/dumb-init", "node", "server/server.js"]
 
 FROM release AS nightly
 RUN npm run mark-as-nightly