docs(doc): add description in README.md (#27)

* docs(doc): add description in README.md

* fix(doc): modify content of README.md from Xiaofei's suggestion

Author: goatman

README.md

@@ -1 +1,5 @@
-# protogen-go
+# Go generated proto packages
+
+> IMPORTANT This repository is currently experimental.
+
+This repository contains the generated Go packages from this [Protobufs](https://github.com/instill-ai/protobufs) for common protocol buffer types, and the generated gRPC code necessary for interacting with Instill AI's gRPC APIs.