fix: automatically inserts an empty text node after inserting an image

[CaptainCrouton89]

Description
Automatically adds an empty text node after inserting an image in the example code for using images in Slate.

Issue
Fixes #5597

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]

⚠️ No Changeset found

Latest commit: f162dee

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[dylans]

Thanks for the fix @CaptainCrouton89

[dylans]

@CaptainCrouton89 see the quick suggested changes by Prettier. Thanks.

[dylans]

suggested changes from prettier

[CaptainCrouton89]

Thanks for fixing that! Glad it's making it in :)