Sous-titres dans les projets et les actualités (#659)

assets/sass/_theme/blocks/posts.sass

assets/sass/_theme/blocks/projects.sass

assets/sass/_theme/design-system/hero.sass

assets/sass/_theme/sections/events.sass

assets/sass/_theme/sections/posts.sass

assets/sass/_theme/sections/projects.sass

layouts/partials/blocks/templates/posts/highlight.html

layouts/partials/blocks/templates/posts/large.html

layouts/partials/blocks/templates/projects/large.html

layouts/partials/posts/hero-single.html

layouts/partials/posts/post.html

layouts/partials/projects/hero-single.html

layouts/partials/projects/project.html