Allow cropping of images from inside the content editor

[mor10]

In user testing, several people have requested the ability to crop images in the editor context after they have been placed. The expectation seems to be that this should be possible, and the abstraction of having to go to the edit media panel to do this results in the user having to crop the image multiple times to "get it right".

This suggestion has several significant sticking points:

1. The idea of cropping images to "fit" within the context of content makes no sense when considering RWD.
2. Users who crop images also expect to be able to uncrop them later or in other contexts when the image is reused.
3. Hard cropping images by changing the file is becoming a somewhat archaic practice thanks to CSS masking and cropping.

Possible solutions:

1. Provide tools for theme developers to provide display sizes and shapes for images in the editor through CSS and take full advantage of RICG image scaling (related to #35094).
2. Allow "soft" cropping through CSS (introduces complications with RWD, but better than hard cropping).
3. Disallow cropping at all.

[mikeschroder]

Hey @mor10! Thanks for this report!

Saw this as we are going through triage. I agree this should be a feature in WordPress. Do you think at this point it belongs more in a Gutenberg ticket, or it'd make sense to leave this one open, and open one in Gutenberg as well, if there isn't already one?

[mor10]

I opened a duplicate ticket on Gutenberg:

​https://github.com/WordPress/gutenberg/issues/13748