Added

• Allow exporting CSS rules from code manager by using json option.
  editor.CodeManager.getCode(component, 'css', { json: 1 })
• Generate CSS code from the array of rules in code manager.
  editor.CodeManager.getCode(null, 'css', { rules: [...] })
• Added editor.addStyle method
• Added editor.getEditing method

Fixed

• Fix error when adding iframe as HTML code #3575
• Fix activatable blocks on drop #3579
• Don't escape textnodes in script components #3620
• Escape asset rendering #3596
• Update style manager properties on dragMode change #2374