Document the limitations around MySQL snapshot schema changes

Author: ilidemi

docs/integrations/data-ingestion/clickpipes/mysql/schema-changes.md

@@ -19,6 +19,10 @@ ClickPipes for MySQL can detect schema changes in the source tables and, in some
 | Adding a new column with a default value (`ALTER TABLE ADD COLUMN ... DEFAULT ...`) | Propagated automatically. The new columns will be populated for all rows replicated after the schema change, but existing rows won't show the default value without a full table refresh |
 | Dropping an existing column (`ALTER TABLE DROP COLUMN ...`)                         | Detected, but **not** propagated. The dropped columns will be populated with `NULL` for all rows replicated after the schema change                                                                |
 
+:::note
+Column additions during snapshot are currently not supported. The suggested workaround is to perform snapshots before or after planned schema changes, or, if the ClickPipe is already failing, to manually add a column of the appropriate type to the destination table.
+:::
+
 ### MySQL 5.x limitations {#mysql-5-limitations}
 
 MySQL versions older than [8.0.1](https://dev.mysql.com/blog-archive/more-metadata-is-written-into-binary-log/) do not include full column metadata in the binlog (`binlog_row_metadata=FULL`), so ClickPipes tracks columns by ordinal position. This means: