There were three problems preventing drag-and-drop in IE:
* IE [doesn't consider contentEditables as inputs](https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/913982/) when it comes to calling `onDrop`.
* Setting `dropEffect` causes an `unspecified error`.
* You can only get a cursor position from a point with `createTextRange` and `moveToPoint`. Also, `moveToPoint` raises an error if it's called during a dropEvent.
This is the start of a glossary in the docs for terms that folks might not know when first learning Slate. Hopefully it makes it easier to learn. If anyone wants to help fill it out, that would be amazing. Thanks!
* Preparing tests
* splitNode replacement
* Remove slow splice; replace mergeNode
* normalize Leaves
* Partially remove characters
* Partially remove characters
* styling
* Fix bugs; almost all characters are replaced
* Fixes almost existing tests; preparing adding tests for text
* Remove un-necessary check
* Empty leaf
* fix characters in getMarks
* Faster fromJSON
* Some corner cases for empty text
* Fix naive bug
* Supporting empty text with marks
* Supporting empty text with marks in hyperscript
* changes tests for marks in empty text
* Support splitNode marks with empty text
* Add tests for splitNode->insert
* Faster removeText
* Add warning ; remove getMarksAtIndex cache
* Remove characters in getInsertMarkAtRange
* Adding tests
* Change names of tests
* Update marks test
* Add a test confirm for invalid offsets:
* Add test for get active marks between offsets
* Fix document
* Add testing for insert-text
* Better remove text
* More sensible marks in empty text
* Allow marks of empty text after deleting partially marked text
* Add test for removing on partially marked text
* chnage test structure
* Add test for removeText
* Add test for removeText
* Avoid conflict between empty marked text and cursor
* Simple style fixes
* Simple style fixes
* Line break fixes
* Line break fixes
* Annotate the createLeaves
* Line breaks in test
* Line breaks fix
* add add-marks test
* add merge test
* Fix version update
* Remove empty_leaf optimization; optimize of that will be other PRs
* Clean up getMarksAtPosition
* Fix get-insert-marks-at-range
* clean up get-marks-at-position
* Fix spaces
* initial simple decorations (mark-like), many tests added
* allow decorators to be set by focus, anchor tags - add tests
* handle one more edge case with decorations in hyperscript
* apply prettier cleanup
* apply linting rules
* update changelog
* ensure always normalize decoration ranges
* reapply prettier after latest adjustments
* all operations apply now update decorations with selection
* ranges can now be 'atomic', will invalidate if contents change
* lint, prettier cleanups
* add atomic invalidation tests, update hyperscript usage
* fix linter errors
* minor cleanup
* slight refactor for simplicity
* remove a couple superfluous lines
* update in response to review
* drop unnecessarily committed add'l file
* remove the need for explicit anchor, focus prop on decoration tags
* update hyperscript use to match latest syntax in #1777
* atomic -> isAtomic
* Fix issue with pasting in IE11
Fixing the issue where dataTransfer or clipboardData are not populated,
in IE 11 under event.NativeEvent. Instead, if we are using IE11, use
the base event object instead which contains a valid dataTrasnfer/clipboardData object.
* Run prettier on code changes
