instead make it invisible setting spacer `color` property to `transparent`.
In Chrome, replace zero-with space with hair space to avoid graphics glitches.
Update tests.
* Add `data-slate-content` attribute to the divs used to render `content` components.
Use that attribute to uniquely identify them.
Update test expected results.
* Fix lint complaints.
* Add base tests for isVoid with around text node
* Ensure that void nodes are surrounded by text nodes in Node.normalize
* Only wrap inline void nodes with text
* Fix indentation
* Add emojis example
* Adapt unit test "transforms/fixtures/at-current-range/set-inline/with-is-void"
* Adapt unit test "transforms/fixtures/at-current-range/insert-inline/with-inline"
* Adapt unit test "transforms/fixtures/at-current-range/insert-inline/block-start"
* add passing parent to leaf nodes, for rendering breaks
* add zero-width spaces in empty text nodes, to allow selections
* add zero-width space handling to copy/cut
* fix delete handling around inline void nodes
* fix tests for inline void nodes
* fix style
* fix void cursor handling across browsers
* fix void rendering tests
* Add property textAlignment for the whole editor
* textAlignment should be set on Content
* Add basic for directionMap in State
* Add RTL to example
* Use setDocument for updating direction map when inserting blocks
* Remove debug log
* Only add 'dir' to node when is not default value
* Prevent tests from failing because of .DS_Store on OSX
* Add tests for rtl rendering
* Fix rendering tests
* Fix test for rendering "text-direction"
* Remove textAlignment prop on editor
* Don't use a directionMap but directly a "textDir" on nodes
* Remove .setDocument from State
* Switch rendering of leaf to use mark as component
* Backward compatibility with renderMark
Don’t fail on null marks
* Adapt tests for new rendering of marks
* Fix selection with new rendered marks
* Adapt rendering test for custom-mark-multiple
Don’t add span when renderMark return undefined
