Implement attachToAll() method using the new editor instance reference API

[oleq]

Thanks ckeditor/ckeditor5-core#184 we can use domEditableElement.ckeditorInstance to get the editor instance. CKEditorInspector.attachToAll() would do:

const editables = document.querySelectorAll( '.ck-editable' );

for ( editable of editables ) {
    if ( not already attached to editable.ckeditorInstance ) {
        CKEditorInspector.attach( editable.ckeditorInstance );
    }
} 

to attach all editor instances automatically. That would be helpful:

• in manual tests, because ATM we only discover window.editor and if there is more than a single editor, it's not inspected out-of-the-box. Note that we need a flag like window.CKEditorInspectorDontAttachAll so in some tests we can disable this feature.
• in bookmarklets

[pomek]

Note that we need a flag like window.CKEditorInspectorDontAttachAll so in some tests we can disable this feature.

CKEditorInspector.disableAttachToAll = true

or something like that. We don't need to use the global scope for that.

[oleq]

It depends on the order of execution. Not sure if window.CKEditorInspector namespace would be available at that particular moment when the flag is to be set.

[pomek]

You're right, good point. What about element custom attrs ([data-ckeditor5-inspector="false"])?

[oleq]

You're right, good point. What about element custom attrs ([data-ckeditor5-inspector="false"])?

What about the ClassicEditor?