add a proper subtitle

src/main/resources/assets/naturesaura/lang/en_US.lang

@@ -35,6 +35,7 @@ container.naturesaura.altar.name=Natural Altar Infusion
 
 info.naturesaura.aura_in_area=Aura Around
 info.naturesaura.book.landing=$(aura) is a complicated matter, and creating, collecting and making use of it can be difficult.$(br)The $(item)Book of Natural Aura$() contains all the information one requires to do so.
+info.naturesaura.book.subtitle=The guide to Nature's Aura
 
 advancement.naturesaura.root=Nature's Aura
 advancement.naturesaura.root.desc=Becoming a magical botanist

src/main/resources/assets/naturesaura/patchouli_books/book/book.json

@@ -9,7 +9,7 @@
     "book_texture": "naturesaura:textures/gui/book",
     "filler_texture": "naturesaura:textures/gui/book_filler",
     "model": "naturesaura:book",
-    "subtitle": "Haha yes",
+    "subtitle": "info.naturesaura.book.subtitle",
     "macros": {
         "$(thing)": "$(#ff6600)",
         "$(item)": "$(#ad09e2)",