Add Anchor Block Support and Vertical Alignment capability

[aurooba]

Closes #5

• This PR adds anchor support to both Super List and Super List Item block.
• There is also a slight visual adjustment to the Super List block inserter, to make it a little smaller but still obvious and easy to click on.
• This PR also adds the Vertical Alignment capability to the overall super list. It does not as of yet, allow you to control vertical alignment on individual Super List Items – that would be part of a larger conversation connected to this comment about layout capabilities.

As far as the Vertical Alignment feature goes:

This is ready and I've done some preliminary testing. But it needs to be tested a bit more to ensure there won't be that Block Recovery error on existing super lists. I've set it up so that the justification settings only add classes IF a justification is set, so theoretically that means there should be no errors on past blocks that don't have anything set. But I'd like to test it a bit more before merging.

• Test on online installations where I have the v0.1.0 installed to check if justification addition causes an error.