* Fix building with Jekyll on Ruby 3.4
Ruby 3.4 removed several standard library packages, so they have
to be installed as gems instead.
This also updates Jekyll to use a version that's supported in Ruby 3.4.
The minimum required Ruby version is now 3.2.
* Fix Sass deprecations
This allows the website to build on Ruby 3.4.0 + Jekyll 4.4.1.
More information:
- https://sass-lang.com/blog/import-is-deprecated/
b42580d8cc
