Wagtail-react-streamfield

- Makes block type styling consistent
- Maximizes the action buttons padding

- Changes the teal color to the new color from Wagtail 2.3
- Improves margins and paddings consistency with Wagtail
- Fixes an issue on mobile devices with the panel for adding new blocks
that jumps during its transition

- Improves mobile layout
- Enlarges the clickable area of add buttons

- Fixes a bug where `COLLAPSIBLE` blocks
couldn’t be defined as open by default
- Fixes the version number

- Changes the overall look to match latest design decisions
- Adds the `SIMPLE` layout
- Makes `SIMPLE` the new default layout
for a better continuity with the old StreamField
- Allows to customize the layout by overwriting
the `Block.get_layout()` method
- Use Wagtail icons instead of FontAwesome icons
- Fixes the remaining CSS integration issues

- Adds Wagtail 2.3 support
- Adds support for block groups
- Adds support for static blocks
- Upgrades to react-beautiful-dnd 10, improving fluidity by 30%