Fix some typos, improve some descriptions

_data/features.json

@@ -1,7 +1,7 @@
 [{
 	"title": "Multi language support",
 	"image": "translations.png",
-	"description": "Vocaluxe supports many different languages - If your language isn't avaialable just start translating it!"
+	"description": "Vocaluxe supports many different languages - If your language isn't available just start translating it!"
 },
 {
 	"title": "Party modes",