docs: add information on what data are collected for tabby server (#520)

website/docs/configuration.md

@@ -23,6 +23,22 @@ Tabby collects usage stats by default. This data will only be used by the Tabby
 
 ### What data is collected?
 We collect non-sensitive data that helps us understand how Tabby is used. For now we collects `serve` command you used to start the server.
+As of the date 10/07/2023, the following information has been collected:
+
+```rust
+struct HealthState {
+    model: String,
+    chat_model: Option<String>,
+    device: String,
+    arch: String,
+    cpu_info: String,
+    cpu_count: usize,
+    cuda_devices: Vec<String>,
+    version: Version,
+}
+```
+
+For an up-to-date list of the fields we have collected, please refer to [health.rs](https://github.com/TabbyML/tabby/blob/main/crates/tabby/src/serve/health.rs#L11).
 
 ### How to disable it
 To disable usage collection, set the `TABBY_DISABLE_USAGE_COLLECTION` environment variable by `export TABBY_DISABLE_USAGE_COLLECTION=1`.