I built a GitHub repository template which automates the process of configuring a new repository to take web page screenshots using GitHub Actions.
You can try this out at https://github.com/simonw/shot-scraper-template
Use the https://github.com/simonw/shot-scraper-template/generate interface to create a new repository using that template, and paste the URL that you want to take screenshots of in as the "description" field.
The new repository will then configure itself using GitHub Actions, take the screenshot and save it back to the repo!
HN post about this from yesterday (which failed to get any traction): https://news.ycombinator.com/item?id=30667588