Add end slide to PPTX

[pjsier]

PPT should have an end slide, probably just recapping the front slide, but with our website link prominent. Feels like it ends a bit abruptly, and having this closing slide to remind people of the site and bookend things seems nice.

From @james-minton on Slack

[pjsier]

@james-minton I'm wondering if we can add this, and use a small section of it as a legend for the exclamation point icons? We don't have a whole lot of space on the PowerPoint for additional description, so adding the icons in context and then explaining them later seems like a good option