Pause menu functionality (#89)

* make menu use actual soundsettings values
* allow changing volume in pause menu
* persist saving settings

Cargo.toml

@@ -56,6 +56,10 @@ bevy_asset_loader = "=0.24.0-rc.1"
 bevy_ballistic = { git = "https://github.com/rustunit/bevy_ballistic.git", rev = "b08ffec" }
 bevy_common_assets = { version = "0.14.0", features = ["ron"] }
 bevy_debug_log = { git = "https://github.com/rustunit/bevy_debug_log.git", rev = "86051a0" }
+bevy_pkv = { version = "0.14", default-features = false, features = [
+    "bevy",
+    "redb",
+] }
 bevy_replicon = "0.37.1"
 bevy_replicon_renet = "0.13.0"
 bevy_sprite3d = "7.0.0"