Update s6-overlay and move processes to new format

docker/rootfs/etc/s6-overlay/s6-rc.d/backend/run

@@ -0,0 +1,19 @@
+#!/command/with-contenv bash
+# shellcheck shell=bash
+
+set -e
+
+echo "❯ Starting backend ..."
+if [ "$DEVELOPMENT" == "true" ]; then
+	cd /app || exit 1
+	# If yarn install fails: add --verbose --network-concurrency 1
+	yarn install
+	node --max_old_space_size=250 --abort_on_uncaught_exception node_modules/nodemon/bin/nodemon.js
+else
+	cd /app || exit 1
+	while :
+	do
+		node --abort_on_uncaught_exception --max_old_space_size=250 index.js
+		sleep 1
+	done
+fi

docker/rootfs/etc/s6-overlay/s6-rc.d/backend/type

@@ -0,0 +1 @@
+longrun