Add rudimentary change log

Author: gvanrossum-ms

CHANGELOG.md

@@ -0,0 +1,15 @@
+# Typeagent Change Log
+
+## 2025
+
+### 0.3.1 (Oct 22)
+
+- Limit dependencies to what's needed at runtime;
+  dev dependencies can be installed separately with
+  `uv sync --extra dev`.
+- Add `endpoint_envvar` arg to `AsyncEmbeddingModel`
+  to allow configuring a non-standard embedding service.
+
+### 0.3.0 (Oct 17)
+
+- First public release, for PyBay '25 talk