add notice about annotation tool being refactored (#262)

docs/user_guide/annotation_tool.md

@@ -1,5 +1,9 @@
 # The Neurobagel Annotation Tool
 
+!!! info
+    This tool is currently undergoing a major refactor - some of the information below may be out of date with the public version of the tool at [https://annotate.neurobagel.org](https://annotate.neurobagel.org/). 
+    Please check back soon for updated documentation!
+
 Neurobagel's annotation tool takes BIDS-style [phenotypic data](https://github.com/neurobagel/annotation_tool/blob/master/cypress/fixtures/examples/good/ds003653_participant.tsv) and [corresponding data description files](https://github.com/neurobagel/annotation_tool/blob/master/cypress/fixtures/examples/good/ds003653_participant.json) and gives users the ability to annotate their data using the Neurobagel data model for preparation to inject that modeled data into Neurobagel's graph database for [federated querying](https://github.com/neurobagel/query-tool).
 
 The annotation tool is a Vue application, developed in [JavaScript](https://www.javascript.com/) using a variety of tools including [Nuxt](https://nuxtjs.org/), [Cypress](https://www.cypress.io/), and [BootstrapVue](https://bootstrap-vue.org/docs).