Refactor README to clarify language version differences.

Author: yegor256

README.md

@@ -1,8 +1,13 @@
-# The "Reducing Programs to Objects" Paper in LaTeX
+# Reducing Programs to Objects
 
 [![arXiv](https://img.shields.io/badge/arXiv-2112.11988-green.svg)](https://arxiv.org/abs/2112.11988)
 [![make](https://github.com/yegor256/reducing-programs-to-objects/actions/workflows/latexmk.yml/badge.svg)](https://github.com/yegor256/reducing-programs-to-objects/actions/workflows/latexmk.yml)
 
+> [!WARNING]
+> This paper describes an earlier version of EO, where we had the `cage` object.
+> The current version of the language is different.
+> The paper needs serious re-writing.
+
 The paper is published in [arXiv] (the draft is in this [PDF]).
 
 To build it, just run:
@@ -20,7 +25,7 @@ and
 [`texqc`](https://rubygems.org/gems/texqc)
 installed.
 
-Once compiled and packaged, upload zip archive to [arXiv].
+Once compiled and packaged, upload the zip archive to [arXiv].
 
 [PDF]: https://github.com/objectionary/reducing-programs-to-objects/blob/gh-pages/paper.pdf
 [arXiv]: https://arxiv.org/abs/2112.11988