add dummy presale dates

docs/timeline.md

@@ -2,8 +2,11 @@
 
 | Date | Description |
 | :--- | :--- |
+|  | Sale of first ticket batch |
 | 09.06. | [Call for Participation](https://events.ccc.de/2023/05/09/camp23-call-for-participation/) Deadline |
+|  | Sale of second ticket batch |
 | 15.06. | [Call for Art](https://events.ccc.de/2023/04/28/camp23-call-for-art/) Deadline |
+|  | Sale of last ticket batch |
 | 30.06. | [Village Registration]() Deadline
 |  | (early) Buildup: Only for people who registered with the orga before.<br />Do not show up unannounced. You will be asked to leave. |
 |  | Buildup: Only for people who help with buildup |