Implement a toolbar component to put the block formatting controls.

API:

• Blocks/components should be able to use the same API/code to define their toolbar

UI:

• The toolbar should stay attached to the bottom of the screen, or the top of the keyboard when visible.
• If the toolbar contains more buttons than fit in the screen width, the user should be able to scroll
• When the keyboard is visible, the toolbar should show a button that allows to toggle/hide the keyboard

What we're not doing as part of this issue (but good to keep in mind):

• Inserter button: that will be part of the Inserter task Inserter #58
• Undo/redo buttons: that will be part of the undo/redo task Undo and redo #171

Tasks

Slot/Fill pattern with Toolbar (1 week)

• Fix : is block focused logic on Android platform
• Implement Slot/Fill "portal" pattern in gutenberg mobile
• Test Slot/Fill pattern with existing InlineToolbar
• Create Toolbar container with Format Toolbar Slot and Heading Toolbar Slot on top of the screen
• Test Slot/Fill pattern with Format Toolbar Slot and existing Format Toolbar

Context (Consumer, Provider) pattern with Toolbar (3 days)

• Provide isSelected logic to Toolbar level

Toolbar Style (2 days)

• Implement toolbar button style by specs
• Implement toolbar style by specs

Keyboard with Toolbar (4 days)

• Move Toolbar to the bottom of the screen and make it keyboard sticky
• Create Keyboard control with the corresponding Slot
• Implement keyboard toggle functionality

Tests (3 days)

• Make proper tests