docs: add warning to install page

docs/install/index.md

@@ -2,6 +2,14 @@
 
 You can use either [Docker](docker) (recommended) or your [local Node.js](local) installation.
 
+::: warning ass 0.15.0 is experimental
+Branch [`dev/0.15.0`](https://github.com/tycrek/ass/tree/dev/0.15.0/) is a full rewrite of the ass codebase.
+
+At this time, it is working and ready for testing, **but is very incomplete** and is lacking many features currently found in ass 0.14.
+
+**The existing configs, data.json, and auth.json will be abandoned. There is currently no migration nor one planned.**
+::::
+
 ## Alternatives
 
 These are not officially supported.