Add SDH-GameSync v1.0.0

Author: AkazaRenn

.gitmodules

@@ -262,4 +262,7 @@
 	url = https://github.com/hyacz/decky-zerotier.git
 [submodule "plugins/decky-virtual-surround-sound"]
 	path = plugins/decky-virtual-surround-sound
-	url = https://github.com/DeckSettings/decky-virtual-surround-sound.git
+	url = https://github.com/DeckSettings/decky-virtual-surround-sound.git
+[submodule "plugins/SDH-GameSync"]
+	path = plugins/SDH-GameSync
+	url = https://github.com/AkazaRenn/SDH-GameSync.git