Update README

Author: davidbrochart

README.md

@@ -3,4 +3,34 @@
 
 # jupyter_ydoc
 
-Document structures for collaborative editing using Ypy
+`jupyter_ydoc` provides [Ypy](https://github.com/y-crdt/ypy)-based data structures for various
+documents used in the Jupyter ecosystem. Built-in documents include:
+- `YFile`: a generic text document.
+- `YNotebook`: a Jupyter notebook document.
+
+These documents are registered in an entry point under the `jupyter_ydoc` group as `"file"` and
+`"notebook"`, respectively. You can access them as follows:
+
+```py
+import sys
+import jupyter_ydoc
+
+# See compatibility note on `group` keyword in https://docs.python.org/3/library/importlib.metadata.html#entry-points
+if sys.version_info < (3, 10):
+    from importlib_metadata import entry_points
+else:
+    from importlib.metadata import entry_points
+
+ydocs = {ep.name: ep.load() for ep in entry_points(group="jupyter_ydoc")}
+print(ydocs)
+# {'file': <class 'jupyter_ydoc.ydoc.YFile'>, 'notebook': <class 'jupyter_ydoc.ydoc.YNotebook'>}
+```
+
+The `jupyter_ydoc` entry point group can be populated with your own document, e.g. by adding the
+following to your package's `setup.cfg`:
+
+```
+[options.entry_points]
+jupyter_ydoc =
+    my_document = my_package.my_file:MyDocumentClass
+```

jupyter_ydoc/__init__.py

@@ -1,3 +1 @@
-from .ydoc import YFile, YNotebook  # noqa
-
 __version__ = "0.1.0"