Explicit and inherited placeholders

Both placeholder paths still work, but inheritPlaceholder now makes the most sense on a textarea, which matches the current test coverage in the Bootstrap 5 build.

Explicit placeholder

Inherited placeholder from textarea

Example configuration - Placeholders

summernote.create('#placeholder-editor', {
  height: 220,
  placeholder: 'Start typing your release note...',
});

summernote.create('#inherited-placeholder-editor', {
  height: 220,
  inheritPlaceholder: true,
});