docs: update README (#42)

Author: mtth

README.md

@@ -1,11 +1,18 @@
 # `git-draft(1)` [![CI](https://github.com/mtth/git-draft/actions/workflows/ci.yaml/badge.svg)](https://github.com/mtth/git-draft/actions/workflows/ci.yaml) [![codecov](https://codecov.io/gh/mtth/git-draft/graph/badge.svg?token=3OTKAI0FP6)](https://codecov.io/gh/mtth/git-draft) [![Pypi badge](https://badge.fury.io/py/git-draft.svg)](https://pypi.python.org/pypi/git-draft/)
 
 > [!NOTE]
-> WIP: Not quite functional yet.
+> WIP: Unstable API.
+
 
 ## Highlights
 
-* Concurrent edits. Continue editing while the assistant runs, without any
-  risks of interference.
-* Customizable prompt templates
-* Extensible bot API
+* Concurrent edits.
+* Customizable prompt templates.
+* Extensible bot API.
+
+
+## Installation
+
+```sh
+pipx install git-draft[openai]
+```