add preview branch to docs

README.md

@@ -49,6 +49,7 @@ This image provides various versions that are available via tags. `latest` tag u
 | :----: | --- |
 | latest | Stable Radarr releases |
 | nightly | Nightly Radarr releases |
+| preview | Preview Radarr releases, currently aphrodite |
 
 ## Usage
 

readme-vars.yml

@@ -19,6 +19,7 @@ development_versions: true
 development_versions_items:
   - { tag: "latest", desc: "Stable Radarr releases" }
   - { tag: "nightly", desc: "Nightly Radarr releases" }
+  - { tag: "preview", desc: "Preview Radarr releases, currently aphrodite" }
 
 # container parameters
 param_container_name: "{{ project_name }}"