chore: Update doc to reflect recent improvement (#696) for searching exact matches using composite key via history UI;

Author: azeng-netflix

docs/tooling.md

@@ -297,6 +297,8 @@ We can also search for changes in specific records by their keys.  On each page
 
 ![History Lookup](img/history-lookup.png)
 
+Search for _exact matches_ using composite key is also supported. When search for a composite key, different fields need to be separated by colons.
+
 Clicking on individual records will bring us back to the object diff view page to see what was changed.