feat(highlight): color cell if contains yes,no,?

[jdorel]

[dhruvasagar]

Thanks, not particularly needed, but still a nice touch.

[jdorel]

I was just thinking about it, and maybe a more modular approach could also be useful ? Something like a prefix to define the color :

Should I do a PR like this ?

[dhruvasagar]

@jdorel sure

[Saroth]

@jdorel
I am sorry this PR cause my NVim very slow when I enable the Table Mode in a markdown file. The .md file has about 20 tables.
I revert the commit 0fe6bd8, and now works well.
This PR may improve performance, I will try later... :)

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My vim version is NVIM v0.5.1.