readme: add some info

Author: efiop

README.rst

@@ -34,8 +34,18 @@ Iterative Telemetry
 Features
 --------
 
-* TODO
-
+* can be disabled in all tools by setting `ITERATIVE_DO_NOT_TRACK=1` env var
+* single anonymised `user_id` across all `iterative` projects
+* collects minimal amount of anonymised data. For example:
+```
+{
+    "tool_name": "dvc",
+    "tool_version": "2.14.0",
+    "user_id": "e798d2e2-8941-4f24-a868-3adcbf6467df",
+    "os_name": "mac",
+    "os_version": "21.4.0",
+}
+```
 
 Requirements
 ------------