Support for excluding any block

[i-am-chitti]

Is your feature request related to a problem? Please describe.
Currently, defaultBlockSpecs has heading, paragraph, bulletListItem, numberedListItem, image and table. So, when a editor is rendered, one can choose any of these blocks. But it would be great to provide ability to exclude some of the default blocks. For example, exclude the image block. A user should not be able to use an image block.

Describe the solution you'd like
Haven't thought. Let's discuss and deduce a solution.

Describe alternatives you've considered
Tried the schema with excluded image block in defaultBlockSpecs but it didn't work.

Additional context
None

[YousefED]

I thought your listed alternative should work. We'll check this out and add a related example.

Related: #401