Add note in README about deprecation

README.md

@@ -1,3 +1,12 @@
+# This package has moved!
+
+`cellfinder-core` has merged with it's napari plugin and is now available as a [single package called `cellfinder`](https://github.com/brainglobe/cellfinder).
+We recommend you uninstall `cellfinder-core` and instead use the functionality provided in the `cellfinder` package.
+
+These changes are part of our [wider restructuring](https://brainglobe.info/blog/version1/version_1_announcement.html) of the BrainGlobe suite of tools and analysis pipelines, which you can [keep up to date with on our blog](https://brainglobe.info/blog/index.html).
+
+---
+
 [![Python Version](https://img.shields.io/pypi/pyversions/cellfinder-core.svg)](https://pypi.org/project/cellfinder-core)
 [![PyPI](https://img.shields.io/pypi/v/cellfinder-core.svg)](https://pypi.org/project/cellfinder-core)
 [![Downloads](https://pepy.tech/badge/cellfinder-core)](https://pepy.tech/project/cellfinder-core)