docs: tag performance improvement note with v7.4.0

Author: krisk

docs/performance.md

@@ -38,7 +38,7 @@ The index stores processed string values and metadata for each key of each item.
 
 ## Guidelines
 
-::: tip Recent improvements
+::: tip New in v7.4.0
 Index creation is now **~30% faster** for object collections and **~60% faster** for string lists, thanks to zero-allocation word counting, pre-allocated record arrays, and tighter loops during index construction.
 :::