Add CI jobs to diff against the deployed version

[PeterJCLaw]

This is expected to be useful when updating dependencies, to ensure that nothing unexpected has changed, or when otherwise making changes to the build system (for the same reason).

[github-actions[bot]]

Build has no changes.

[github-actions[bot]]

🔀 Build diff:

diff -ru main/feed.xml local/feed.xml
--- main/feed.xml   2024-06-03 20:14:56.639248497 +0000
+++ local/feed.xml  2024-06-03 20:14:16.000000000 +0000
@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?><feed xmlns="http://www.w3.org/2005/Atom" ><generator uri="https://jekyllrb.com/" version="3.9.5">Jekyll</generator><link href="https://studentrobotics.org/website/feed.xml" rel="self" type="application/atom+xml" /><link href="https://studentrobotics.org/website/" rel="alternate" type="text/html" /><updated>2024-06-03T21:14:19+01:00</updated><id>https://studentrobotics.org/website/feed.xml</id><title type="html">Student Robotics</title><subtitle>Student Robotics is an exciting annual competition challenging people aged 16-19 to assemble a team and build fully autonomous robots.
+<?xml version="1.0" encoding="utf-8"?><feed xmlns="http://www.w3.org/2005/Atom" ><generator uri="https://jekyllrb.com/" version="3.9.5">Jekyll</generator><link href="https://studentrobotics.org/website/feed.xml" rel="self" type="application/atom+xml" /><link href="https://studentrobotics.org/website/" rel="alternate" type="text/html" /><updated>2024-06-03T21:14:15+01:00</updated><id>https://studentrobotics.org/website/feed.xml</id><title type="html">Student Robotics</title><subtitle>Student Robotics is an exciting annual competition challenging people aged 16-19 to assemble a team and build fully autonomous robots.
 </subtitle><entry><title type="html">Gymnasium Markt Indersdorf win Student Robotics Competition 2024!</title><link href="https://studentrobotics.org/website/blog/2024-04-18-mai-win-sr2024/" rel="alternate" type="text/html" title="Gymnasium Markt Indersdorf win Student Robotics Competition 2024!" /><published>2024-04-18T00:00:00+01:00</published><updated>2024-04-18T00:00:00+01:00</updated><id>https://studentrobotics.org/website/blog/mai-win-sr2024</id><content type="html" xml:base="https://studentrobotics.org/website/blog/2024-04-18-mai-win-sr2024/">&lt;figure class=&quot;&quot;&gt;

   &lt;a href=&quot;/website/images/content/blog/sr2024/sr2024-photo.large.jpg&quot;&gt;