Creating lists is painful

[auryn-macmillan]

Describe the bug
Creating lists (both ordered an unordered) currently requires each line to be manually selected and set to a list.

To Reproduce
Steps to reproduce the behavior:

1. open a new draft
2. select list or ordered list from the block picker
3. type something for your first list item
4. press [enter]/[return] to move to your second list item
5. Notice that the new line is a separate block and is set to paragraph, you must open the block picker and select one of the list types in order to continue your list.

Expected behavior
If you are editing a list item:

• pressing [enter]/[return] should move insert a new item to your list immediately below the current line.
• pressing [shift]+[enter] should move to a new line in the same block, rather than creating a new block. This and all subsequent lines in the same block as the list element should maintain the same indentation as the first line in the block.
• pressing [backspace] with the cursor in the first position on a list item should convert the block to a paragraph.