bad link

[CerebralMastication]

trafficstars

in page: https://course.fast.ai the link in the text Start watching [lesson 1](https://course.fast.ai/Lessons/lesson1.md) now! returns 404. This link is present ~7 times (!) on that page.

Possibly the proper link is https://course.fast.ai/Lessons/lesson1.html ... note the html extension instead of md

after some browsing I see this bad link is everywhere. For example https://course.fast.ai/Resources/testimonials.html so better run that regex on the whole site