Support ESLint comment

[azu]

We want to support <!-- eslint-disable no-alert --> for compatibility eslint/eslint-plugin-markdown

[JounQin]

But eslint-plugin-markdown doesn't support disabling Markdown (HTML) comments for ignoring some CodeBlocks.

It seems not true after eslint-plugin-markdown@1.

[azu]

https://github.com/eslint/eslint-plugin-markdown#configuration-comments
I see. we need to update README.