stop scroll to top on md preview
stop scroll to top on md preview

rough proof of concept: use html bc faster, and only show loaded when
page first loads

rugk/markdown-preview,Galadirith/markdown-preview,makyo/markdown-preview,ArnaudRinquin/markdown-preview,atom/markdown-preview,sctlee/markdown-preview,grimmer0125/markdown-preview-kramdown,tkssharma/markdown-preview