Add maintenance notice

Author: johnridesabike

Diff for: README.md

@@ -4,6 +4,18 @@
 <p>Coronate is a web app for managing Swiss-style chess tournaments.</p>
 </div>
 
+## Notice
+
+Maintenance is currently paused for Coronate. This has almost always been a
+one-person passion project, and there simply isn't time to work on it these
+days. The [version hosted here](https://coronate.netlify.app/) should continue
+to work for the indefinite future, and its code will always be open-source.
+Anyone may use the Coronate source code in accordance with its
+[license](./LICENSE).
+
+If you have a special interest in working with Coronate that you wish to
+discuss, please still feel free to reach out to me or open a GitHub issue.
+
 ## About
 
 Coronate is a free chess tournament manager. Anyone, even a tournament newbie