Update readme

Author: jcrist

README.md

@@ -1,9 +1,28 @@
-# Ibis Examples
+# Ibis Example Notebooks
 
 This repository contains runnable example notebooks for
-[Ibis](ibis-project.org/).
+[Ibis](ibis-project.org/). They are intended to be educational and give users
+examples of common Ibis workflows.
 
-They are intended to be run on [mybinder.org](https://mybinder.org) via the
-link below:
+The easiest way to run the notebooks is in the cloud by clicking the link
+below:
 
 [![Binder](https://static.mybinder.org/badge_logo.svg)](https://mybinder.org/v2/gh/ibis-project/ibis-examples/main)
+
+## Contributing
+
+Do you have an interesting example notebook that makes use of `ibis`? Please
+consider submitting it to this repository.
+
+Note that examples should adhere to the following guidelines:
+
+- Run top-to-bottom without error/intervention from the user
+
+- Not require external data sources that are likely to disappear over time
+
+- Not be resource intensive. Currently notebook sessions launched in
+  [mybinder.org](https://mybinder.org) have access to 1-2 GiB of RAM. Your
+  example must be able to run within these restrictions.
+
+- Be *interesting*, *exemplary* of good `ibis` usage, and of *general
+  relevance* to `ibis` users.