runelite-client: add configuration option for resizable

runelite-client/src/main/java/net/runelite/client/config/RuneLiteConfig.java

@@ -44,6 +44,16 @@ public interface RuneLiteConfig extends Config
 		return Constants.GAME_FIXED_SIZE;
 	}
 
+	@ConfigItem(
+		keyName = "isResizable",
+		name = "Enable window resizing",
+		description = "Determines if the window is resizable"
+	)
+	default boolean isResizable()
+	{
+		return true;
+	}
+
 	@ConfigItem(
 		keyName = "uiEnableCustomChrome",
 		name = "Enable custom window chrome",