Update logic for get 'img' form 'figure'.

[kaluginserg]

Update logic for get img form figure view element.
Fix strange behaviour with custom extending plugins with downcasting images attributes.
Issue describes here: ckeditor/ckeditor5#6294

Default behaviour for getting img-view element was : .getChild( 0 ) it is not best when we have some tags before img 'tag'. It can be possible in future...

Suggested behaviour:
Array.from( figureView.getChildren() ).find( viewChild => viewChild.is( 'img' ) );

and encapsulate it to utils function getImgViewFromFigure().

This approach provide ability to extend plugin logic with other custom plugins.

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[kaluginserg]

@Reinmar @dkonopka
continuous-integration build failed - but detailed reason seems not related with MergeRequest itself.
Can you review my Merge Request ?
Thanks.

[jodator]

Hello - thanks for the fix we spotted that error but haven't had a use-case for such extension so it was left as-is.

I didn't check if it solves all of the issues with extending the image feature output, but the change itself looks OK.

If you could add a test for this would be awesome. I'll check this next week after the release process and most likely merge it.

[Reinmar]

As for the CI, please ignore that. It's something we'll need to resolve.

[kaluginserg]

@jodator
About test cases I have no test cases, I think - needs to create some little extender, or sub-plugin, like current figcaption (but added before img tag)...

I can share with you our company concept for title/legends for images/tables, (it is almost work for images, with little bugs, but not work for tables itself, for tables we use this approach with extra-wrapper, because built-in table - hard extensible):
https://gist.github.com/kaluginserg/497d5702d1444d1284f660ec5cc27083

[jodator]

Thank you @kaluginserg for fixing this. I've added one test to this. You can track the next release announcements here: ckeditor/ckeditor5#6317