Use Docker's builtin tini process, to run as PID 1 and handle SIGTERM…

…s/SIGINTs

Fixes #20

docker-compose.yaml

@@ -5,6 +5,7 @@ services:
       context: .
       dockerfile: Dockerfile
     # image: quay.io/invidious/inv-sig-helper:latest
+    init: true
     command: ["--tcp", "127.0.0.1:12999"]
     ports:
       - 127.0.0.1:12999:12999