(_markdown.scss): fix images clipping outside of container
(_markdown.scss): fix images clipping outside of container

As seen on blog post image (home page)

fabd/kanji-koohii,fabd/kanji-koohii,fabd/kanji-koohii,kanji-koohii/kanji-koohii,kanji-koohii/kanji-koohii,kanji-koohii/kanji-koohii,fabd/kanji-koohii,kanji-koohii/kanji-koohii,fabd/kanji-koohii,kanji-koohii/kanji-koohii,fabd/kanji-koohii