Classic Block: Read More tag is missing "More" text label.

[kjellr]

Describe the bug

In the current classic editor, the "More" divider has a text label inside of it, to more clearly convey what the dotted line means:

The classic block removes that label:

I'm unsure if that was intentional or not, but I think including the label would be more clear — the dotted line on its own is confusing.

To Reproduce

1. Add a Classic block
2. Insert a "Read More" tag from the Classic bar's toolbar.

[draganescu]

@kjellr It appears to have been an optimisation of some sort, b/c in the classic editor the more tag used a large image to set that more text on a dashed line while the classic block uses a dashed border. I am looking into using some pseudo element and a wrapper to the image in the classic block to achieve the same effect, or maybe just revert to the old image.