Update & Fix Codespaces / DevContainer build

[rossboast]

This pull request updates and improves the development container for the project. The most important changes include upgrading the Ruby base image, enforcing consistent line endings, updating shell and Ruby settings, and improving local development workflows.

This PR addresses Issue #159.

Development container and environment updates:

• Upgraded the Ruby base image in .devcontainer/Dockerfile from 2.7-bullseye to 3.2-bookworm for improved compatibility and access to newer Ruby features.
• Added a step in .devcontainer/Dockerfile to convert setup.sh line endings from CRLF to LF, and ensured shell scripts and Dockerfiles always use LF endings via .gitattributes for better cross-platform support. [1] [2]

Devcontainer and VS Code customization:

• Updated .devcontainer/devcontainer.json to explicitly set the Dockerfile, customize VS Code extensions and settings (including Ruby LSP options), and add a post-create command to fix gem permissions and run bundle install.

Gem and dependency management:

• Updated the Gemfile to require Jekyll 3.9.5 (from 3.9.2) and added the webrick gem, which is necessary for Ruby 3.x compatibility.

Development workflow improvements:

• Modified the "run locally and watch" task in .vscode/tasks.json to use bundle exec jekyll serve --livereload --force_polling, enabling live reload and more reliable file watching during development.