Add autoscaling documentation and examples for mc-router integration (#3826)

docs/misc/autoscale/autoscale.md

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+
+# Autoscaling (sleep when idle)
+
+Autoscaling (sometimes called *sleeping*, *scale to zero* or *wake on join*) is the pattern of stopping a Minecraft server when nobody is playing and starting it again when someone tries to connect with the intention of saving resources when the server is not in use (e.g., on a VPS with limited CPU/RAM or a home server).
+
+## mc-router
+
+[mc-router](https://github.com/itzg/mc-router) is a Minecraft-aware router/multiplexer.
+
+- Routes players by the hostname they connect with (useful for multiple servers behind one port)
+- Can auto-start a backend container on join and stop it again after an idle timeout
+
+Examples:
+
+- See the mc-router section in [Examples](../examples.md#mc-router-with-auto-scale)
+
+## Lazymc
+
+[Lazymc](https://github.com/timvisee/lazymc) can keep a server “asleep” until a player connects. With Docker it’s commonly used via [lazymc-docker-proxy](https://github.com/joesturge/lazymc-docker-proxy).
+
+- Players connect to the proxy; the proxy starts/stops the server container
+- Usually requires a static IP for the Minecraft container on a user-defined network
+
+Example:
+
+- See the Lazymc section in [Examples](../examples.md#lazymc-put-your-minecraft-server-to-rest-when-idle)
+
+## Lazytainer
+
+[Lazytainer](https://github.com/vmorganp/Lazytainer) starts/stops containers based on network traffic.
+
+- Uses packet thresholds + inactivity timeouts (not Minecraft hostname aware)
+- Can be triggered by port scans/pings in noisy environments
+
+Example:
+
+- See the Lazytainer section in [Examples](../examples.md#lazytainer-stop-minecraft-container-based-on-traffic)
+
+