Previewing posts on Akkoma (#933)

* Previewing posts on Akkoma

* move preview property into status

* clean up code

* revert imm-related changes

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Co-authored-by: sk <sk22@mailbox.org>

mastodon/src/main/java/org/joinmastodon/android/api/requests/statuses/CreateStatus.java

@@ -48,6 +48,8 @@ public class CreateStatus extends MastodonAPIRequest<Status>{
 		public String quoteId;
 		public ContentType contentType;
 
+		public boolean preview;
+
 		public static class Poll{
 			public ArrayList<String> options=new ArrayList<>();
 			public int expiresIn;