Increase the page width to make examples with 100 character widths work

[joshka]

When adding the examples from the main repo to this repo, I hit a small snag - they're all formatted to 100 char widths.
But the website assumes 80. I think in general that's too low and we should be using 100. I initially put the 80 character limit in place to avoid horizontal scrolling in the default page widths, and to avoid having to adjust them. I think it's probably time to adjust the page widths instead.

For context - this is the current layout on my 16in MBP:

Related: #613