emojis: add acorn emoji

The emoji uses the trigger is `<D~`

runelite-client/src/main/java/net/runelite/client/plugins/emojis/Emoji.java

@@ -87,6 +87,7 @@ enum Emoji
 	HEART_EYES("(*.*)"),
 	FACEPALM("M-)"),
 	PENSIVE("V_V"),
+	ACORN("<lt>D~") // <D~
 	;
 
 	private static final Map<String, Emoji> emojiMap;