Integration with code spell checker

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For writing, spell checker is a quite useful tool. But Quarto extension in vscode is not integrated with a spell checker.
In #1218 , one has proposed a solution to use code spell checker extension, which eases the problem to some extent but still has some unsatisfactory points. For example, if one specifies .qmd with quarto spell checker, it will check all the contents of .qmd file. But in most cases, one only needs to check markdown cells, which contain contents for publishing.
So it will be good that quarto extension itself can support markdown cell spell checking.