feat: Write built in themes to the themes file on first run so users can define custom themes

themes/dracula/README.md

@@ -0,0 +1,9 @@
+# Managarr Dracula Theme
+The [themes.yml](./themes.yml) file in this directory corresponds to the theme configuration for the
+Dracula Managarr theme.
+
+## Screenshots
+
+![sonarr-library](./sonarr_library.png)
+![manual-episode-search](./manual_episode_search.png)
+![radarr-system](./radarr_system.png)