Support for decorators when linking images

[pomek]

Suggested merge commit message (convention)

Fix (link): Manual and automatic decorators will work properly with a link that is labeled by an image. Closes #7519.

Internal (link): An icon that indicates that the image is linked will not be displayed in the editor's data. Closes #7626.

☝️ marking as internal since the icon and the bug was introduced in the same iteration.

[jodator]

LGTM, I'd change only how the AutomaticDecorators instance is passed and where it is created.

The other comment about name, location, etc actually is for current implementation but as we already have that let's keep that part consistent.

[confettidc]

Hi all, I have already updated @ckeditor/ckeditor5-link to version 20.0.0, but below problem still persists, can help check?

WhatsApp Video 2020-07-25 at 01.50.06.mp4.zip

CkEditor config (just copied related options):
ClassicEditor.create(document.getElementById( elementId ), {
toolbar: [ 'undo', 'redo', '|', 'indent', 'outdent', 'alignment', 'bold', 'italic', 'underline', '|', 'FontSize', 'FontColor', '|', 'insertTable', 'imageUpload', 'mediaEmbed', '|', 'strikethrough', 'link', 'subscript', 'superscript', 'bulletedList', 'numberedList', 'HorizontalLine'],
link: {
decorators: {
isExternal: {
mode: 'manual',
label: '',
attributes: {
target: '_blank',
rel: 'noopener noreferrer'
}
}
}
},

        image: {
        	toolbar: [ 'imageTextAlternative', '|', 'imageStyle:alignLeft', 'imageStyle:full', 'imageStyle:alignRight', 'linkImage' ],

            styles: [
                // This option is equal to a situation where no style is applied.
                'full',

                // This represents an image aligned to the left.
                'alignLeft',

                // This represents an image aligned to the right.
                'alignRight'
            ]
        },

Thanks.