Add signposting to Run 3 Starterkit

Author: AndyLHCb

README.md

@@ -1,11 +1,13 @@
 # The LHCb Starterkit lessons ![Build Status](https://github.com/lhcb/starterkit-lessons/actions/workflows/build.yml/badge.svg)
 
-These are the lessons taught during the [LHCb Starterkit][starterkit].
+These are the lessons historically taught during the [LHCb Starterkit][starterkit].
+These lessons focus on LHCb software from Runs 1 and 2. For Run 3, the software changed a lot and a [new set of Starterkit lessons][run3-starterkit] was written.
 If you'd like to join the next workshop, visit [the website][starterkit] to find out when that will how and how to sign up.
 
 If you'd just like to learn about how to use the LHCb software, [read on](first-analysis-steps/README.md)!
 
 [starterkit]: https://lhcb.github.io/starterkit
+[run3-starterkit]: https://lhcb-starterkit-run3.docs.cern.ch/
 [first-analysis-steps]: https://lhcb.github.io/starterkit-lessons/first-analysis-steps/
 
 

_templates/layout.html

@@ -0,0 +1,8 @@
+{% extends "!layout.html" %}
+
+{% block content %}
+  {{ super() }}
+  <footer class="custom-footer" style="margin-top: 2em; padding-top: 1em; border-top: 1px solid #ccc; font-size: 0.9em; text-align: center;">
+    <p>Note that this is the Starterkit for Runs 1 and 2. For Run 3, the software changed considerably and you can find its own dedicated Starterkit lessons <a href="https://lhcb-starterkit-run3.docs.cern.ch" target="_blank">here</a>.</p>
+  </footer>
+{% endblock %}

conf.py

@@ -34,6 +34,9 @@
     r'https://sourceforge.net/.*', # 403 error - rejects the bot
 ]
 
+# Add a footer pointing to the Run 3 Starterkit
+templates_path = ["_templates"]
+
 starterkit_ci_redirects['first-analysis-steps/index.html'] = 'https://lhcb.github.io/starterkit-lessons/first-analysis-steps/README.html'
 starterkit_ci_redirects['second-analysis-steps/index.html'] = 'https://lhcb.github.io/starterkit-lessons/second-analysis-steps/README.html'