Website: Add release schedule on the releases page

Author: jbonofre

site/docs/releases.md

@@ -77,6 +77,15 @@ Apache Iceberg 1.4.3 was released on December 27, 2023. The main issue it solves
 - Core: Expired Snapshot files in a transaction should be deleted by [@bartash](https://github.com/bartash) in [#9223](https://github.com/apache/iceberg/pull/9223)
 - Core: Fix missing delete files from transaction by [@nastra](https://github.com/nastra) in [#9356](https://github.com/apache/iceberg/pull/9356)
 
+## Schedule
+
+| Version | Spark Versions | Flink Versions | Java Versions | ETA    |
+|---------|----------------|----------------|---------------|--------|
+| 1.4.3   | 3.3+           | 1.16+          | 8, 11, 17     | Jan 24 |
+| 1.5.0   | 3.3+           | 1.16+          | 8, 11, 17     | Feb 24 |
+| 1.6.0   |                |                |               | May 24 |
+| 1.7.0   |                |                |               | Aug 24 |
+| 1.8.0   |                |                |               | Dec 24 |
 
 ## Past releases