Directly paste ClipboardEvents in Safari

[jason0x43]

Description
This PR changes updates the paste handling code to always use ClipboardEvents in Safari rather than preferring InputEvents as InputEvents won't include files or data items with custom mime types.

Issue
Fixes: #4998

Example
Log the types of the data property passed to ReactEditor.insertData when pasting and verify that with this PR they include application/x-slate-fragment, and without this PR they don't.

Ideally, if a document that has problems copying and pasting in Safari is available, such as one containing inline images, verify that content that normally has problems pastes properly with this PR.

Context
Pasting generates two events in Safari: a ClipboardEvent and an InputEvent. Currently, Slate generally ignores ClipboardEvents in Safari in favor of InputEvents, which flow through Slate's onDOMBeforeInputHandler. This is problematic because InputEvents generated by pasting in Safari are missing some key pieces of data: they won't include files or an application/x-slate-fragment data item. ClipboardEvents do have this data.

Checks

• The new code matches the existing patterns and styles.
• The tests pass with yarn test.
• The linter passes with yarn lint. (Fix errors with yarn fix.)
• The relevant examples still work. (Run examples with yarn start.)
• You've added a changeset if changing functionality. (Add one with yarn changeset add.)

[changeset-bot]

🦋 Changeset detected

Latest commit: ba02b2c

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
slate-react	Patch

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[dylans]

Wow, such a simple fix.

Could you please add a changeset (patch change level) and then I'll land it. Thanks!

[jason0x43]

Changeset added