Add linter for Maximum document length

[gaelj]

✨ Introduce new features

• Add an optional linter for Maximum document length

🐛 Fix a bug

• Don't try to upload files if no callback was defined
• Fix any text was pasted as markdown table
• Fix hitting backspace on line before horizontal rule would delete it
• Fix html rendering of markdown tables skipped empty cells
• Focus the editor when full screen is toggled
• Prevent second scroll bar from appearing depending on the width in fullscreen

📝 Add or update documentation

• Add ReadOnly checkbox to example

🔇 Remove logs

• Don't log full editor text, only length and only if changed