✨ feat(server): Add startup script (#63)

## Description

**What issue are you solving (or what feature are you adding) and how
are you doing it?**

We start the container using supervisord, which is limiting as the user
has no way of telling the container what game to run. So, the idea is to
run like so: `docker run... ghcr.io/netrisdotme/netris/server:<tag>
netris-proton /game/yourgame.exe`


Co-authored by @djpremier

.scripts/startup.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+#TODO: Fix the warp-input startup problem
+if [ -z "$SESSION_ID" ]; then
+    echo "Error: SESSION_ID environment variable is not set."
+    exit 1
+fi
+
+xarg="$*"
+
+if [ -z "$xarg" ]; then
+    echo "Error: No command specified to run the game. Exiting."
+    exit 1
+fi
+ 
+#Open udp port to listed for QUIC events on 
+export PORT=${PORT:-"8080"}
+
+escaped_xarg=$(printf '%s\n' "$xarg" | sed -e 's/[\/&]/\\&/g')
+
+sudo sed -i "s|^command.*=.*$|command=bash -c \"$escaped_xarg\"|" /etc/supervisord.d/game.ini
+
+sudo sed -i 's|^autostart.*=.*$|autostart=true|' /etc/supervisord.d/game.ini
+
+sudo -E /usr/bin/supervisord -c /etc/supervisord.conf