Bubble menu block type dropdown

[YousefED]

Add a dropdown to change the blocktype:

In BlockNote, currently blocks can be both Heading and List at the same time. This means we have two options:

A. Block type dropdown only contains Text / Heading options

• Make the block type dropdown only have options for Text / Heading (1/2/3)
• Add separate menu buttons for the "list type":

Pros:

• user can create all possible block type combinations from the menu

Cons:

• more menu items = more clutter

B. Block type dropdown only contains Text / Heading options

• The dropdown should have options for: Text, Heading 1 / 2 / 3, Bulleted list, Numbered list, To-do list.
• A heading that's also a list, should show as Heading (i.e.: Heading takes precedence)
• When changing block types, drop the other attributes (i.e.: changing a bullet-heading to text, removes both the bullet and the heading attributes, changing a list item to a heading removes the list attribute)

Pros:

• Less menu items = cleaner

Cons:

• Some block types won't be possible to create via the menu, but will be via keyboard (e.g.: when you type "-" in front of a heading

I think option B would have my preference atm, what do you think?

Other notes:

• The menu should display the type of the current element
• The H1 and H2 buttons that are currently in the BubbleMenu can be removed
• You can use the AtlasKit Dropdown menu for this: https://atlassian.design/components/dropdown-menu/examples