Move default media library from static/img/ to static/media/ as it can now contain audio, video, and other kinds of media in addition to images.
BREAKING CHANGE:
Either rename your site's static/img/ to static/media/ (and update any references to this folder in your Markdown files);
Or, add `media_dir = "img"` to `params.toml` to continue using the legacy location.
Also renames Hero Carousel widget to Slider.
BREAKING CHANGES:
- widget `[header]` options removed and replaced with `[background]`
- `hero_carousel` widget renamed to `slider`
Close#948
- Support multiple paragraphs
- Icon support for `[cta]` call-to-action button
- Add optional alternative call-to-action link `[cta_alt]`
- Add optional note underneath cta button
- Add optional image
- Refresh the demo's instance of the Hero widget
Close#935
George Cushen