Clarify desktop documentation and simplify project presentation

docs/README.md

@@ -1,5 +1,10 @@
 # Documentation
 
+These guides describe the development version on `main`.
+For the packaged **0.1.0-beta**, use the
+[release notes](https://github.com/ferese-wm/ferese/releases/tag/v0.1.0-beta)
+and [guides at that tag](https://github.com/ferese-wm/ferese/tree/v0.1.0-beta/docs).
+
 ## Usage
 
 - [Installation](installation.md): install dependencies, log in, preview changes, update and recover a session.