Add an easy to use spellcheck Validated

At the moment, one has to implement a lot of extra code to add a spellcheck to the editor. The editor would be a much better product if you could simply have the spellcheck built in, and turned on by default. One of the core features of a document editor is the spellcheck. 

Regarding Blazor Server, it should simply be a matter of SpellCheck=true. At the moment I have to add another project to support spellchecking!

Also, the documentation barely mentions how to implement spell checking. It's a feature that should be built in by default and explained in the documentation.