improvements for [slug].js

[jonathan-chin]

• [ ] make hero images responsive and keep original aspect ratio
• [ ] switch CKEditor to markdown and render maybe using React Markdown
• [ ] make update time more readable, probably using React Moment or another date utility package
• [ ] fix this error: Warning: Propsrcdid not match. Server: "http://localhost:1337/uploads/stream_starting_soon_d9b7dca817.png" Client: "undefined/uploads/stream_starting_soon_d9b7dca817.png"

[jonathan-chin]

combined with #28