replace default details marker with custom toggle arrows

[BytePaul]

Replace default details marker with custom toggle arrows (▼/▲) and update Gemfile

Description

This PR introduces two improvements:

Custom toggle arrows for

/

• Removed the default browser disclosure marker.
• Added a right-aligned ▼ (closed) and ▲ (open).
• Improves clarity and visual consistency in workshop event sections.

Gemfile update for compatibility

• Updated dependencies to support the latest Ruby/Jekyll versions.
• Resolves issues with outdated versions during local builds.

[MakisH]

Thanks for the PR! Do you have screenshots of how this would look like when rendered? That would make the PR easier to review.

[BytePaul]

Sure!

[MakisH]

The CI is failing to build the website from this PR: https://github.com/precice/precice.github.io/actions/runs/17377997579/job/49330210240?pr=582

[MakisH]

The setup-ruby action fails with:

Installing Bundler
  Using Bundler 2.7.1 from Gemfile.lock BUNDLED WITH 2.7.1
  /opt/hostedtoolcache/Ruby/3.0.7/x64/bin/gem install bundler -v 2.7.1
  ERROR:  Error installing bundler:
  	bundler-2.7.1 requires Ruby version >= 3.2.0. The current ruby version is 3.0.7.220.

The Ruby version is fixed in https://github.com/precice/precice.github.io/blob/master/.ruby-version

You could try updating the version there and see what happens.

[MakisH]

Let's keep the changes to the Gemfile and Gemfile.lock in a separate PR, if they are not needed for the actual feature.

[MakisH]

@BytePaul in the "Files changed" view (https://github.com/precice/precice.github.io/pull/582/files) I now see the changes of this PR and of #584 mixed together. It is important to keep the changes of each PR separate, so that each PR can be reviewed individually. Please drop the unrelated commits.