[ADD] responsive article detail

...ource/_patterns/molecules/articles/article-perex.mustache

...erns/molecules/articles/article-richtext-content.mustache

...source/_patterns/molecules/blocks/block-download.mustache

...de/source/_patterns/molecules/blocks/block-image.mustache

...de/source/_patterns/molecules/blocks/block-quote.mustache

...eguide/source/_patterns/templates/article-detail.mustache

main/styleguide/source/css/atoms/container.pcss

main/styleguide/source/css/atoms/heading.pcss