feat(deps): Adds serde feature to aeronet_steam

[naomijub]

My project uses aeronet steam plugin but we also serialize steam type, if I dont have the option to enable serde on aeronet_steam we wont be able to connect steam with console to share a session

[aecsocket]

you can do this trivially in your own code by

[dependencies]
steamworks = { version = "match the same steamworks version as aeronet_steam", features = ["serde"] }

don't need aeronet_steam to expose this. if your game/app uses steam, then you're probably already depending on steamworks, so just add serde to that