Update README and client documentation

docs/index.md

@@ -12,13 +12,14 @@ a CalDAV/CardDAV server
 
 - easy to backup, everything saved in one SQLite database
   - also export feature in the frontend
-- [WebDAV Push](https://github.com/bitfireAT/webdav-push/) support, so near-instant synchronisation to DAVx5
+- **[WebDAV Push](https://github.com/bitfireAT/webdav-push/)** support, so near-instant synchronisation to DAVx5
 - lightweight (the container image contains only one binary)
 - adequately fast (I'd love to say blazingly fast™ :fire: but I don't have any benchmarks)
 - deleted calendars are recoverable
 - Nextcloud login flow (In DAVx5 you can login through the Nextcloud flow and automatically generate an app token)
 - Apple configuration profiles (skip copy-pasting passwords and instead generate the configuration in the frontend)
-- [OpenID Connect](setup/oidc.md) support (with option to disable password login)
+- **[OpenID Connect](setup/oidc.md)** support (with option to disable password login)
+- Group-based **sharing**
 
 ## Tested Clients
 

docs/setup/client.md

@@ -72,3 +72,9 @@ For group collections explicitly specify
 ```
 https://<your-host>/caldav-compat/principal/<principal>
 ```
+
+## Thunderbird
+
+- Go to `New Account -> Calendar -> On The Network`
+- Specify the root path of RustiCal
+- Thunderbird will properly discover group calendars