add deprecation notice in advance of archiving repo

README.rst

@@ -9,9 +9,15 @@ Homestead-Guide
 .. |Gitter| image:: https://badges.gitter.im/ethereum/homestead-guide.svg
    :target: https://gitter.im/ethereum/homestead-guide?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge
 
-The Ethereum Homestead Guide is the reference documentation accompanying the Homestead release of the Ethereum project. Note that sections of this guide may be outdated. The Guide may be considered to be a historic reference since Ethereum had the Metropolis phase 1 fork, `Constantinople <https://eips.ethereum.org/EIPS/eip-609>`_. An alternative documentation base may be used at https://github.com/ethereum/wiki/wiki ("the Wiki"), which is being actively maintained, and is also freely editable by anyone with a GitHub account (while editing this repo requires making a PR and being merged by a collaborator, or accepting an invitation as a collaborator). Note that documentation in this guide that is still relevant could be moved to the Wiki.
 
-`Hosted on ReadTheDocs`_
+DEPRECATION NOTICE
+==================
+
+The Ethereum Homestead Guide is the reference documentation accompanying the **Homestead release** of the Ethereum project. 
+The information in this repository is largely out of date. Relevant material has been migrated to https://ethereum.org.
+and this repository is **due to be archived shortly**. For current information on Ethereum, please visit https://ethereum.org instead.
+This repository is for historical reference only!
+
 
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