Upgrade github action to use Ruby 3.3

[turegjorup]

According to Claude Coding Agent the error in the github actions builds is a known error

NameError: uninitialized constant JSON::Fragment

This is a known compatibility issue between newer versions of sass-embedded and Ruby 3.1. The problem occurs during the native extension build process.
To fix this, you need to either:
Downgrade sass-embedded (recommended quick fix)
Upgrade Ruby version to 3.2 or higher

This PR updates the ruby version used to 3.3 to resolve the issue (#11).