feat: update font styles and add related events block on install - Replace font-family values with CSS variables in `lb-related-events-block.css` and `lb-related-events-node.css` - Update font-weight in `lb-related-events-block.css` and `lb-related-events-node.css` - Refactor SCSS files to use CSS variables for font-families - Add hook_install function in `lb_related_events_blocks.install` to create and append a new block content on module installation - Update library version in `lb_related_events_blocks.libraries.yml`