Add changelog entry for experimental Lakeflow template (#2979)

## Changes

Add changelog entry for experimental Lakeflow template

## Why
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## Tests
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Co-authored-by: Pieter Noordhuis <pieter.noordhuis@databricks.com>

Author: fjakobs

NEXT_CHANGELOG.md

@@ -9,5 +9,6 @@
 ### CLI
 
 ### Bundles
+* Add an experimental project template for Lakeflow Declarative Pipelines ([#2959](https://github.com/databricks/cli/pull/2959))
 
 ### API Changes