Upgrade `marked` package

[yzhang-gh]

Thanks for this nice project.

The latest marked version is 0.4.0 but we still have 0.3.12 for docsify. It will be nice to upgrade it to the latest version.

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One related issue is the parsing of raw HTML blocks. With the marked online demo, we have this result

However, we get this result with docsify

[yzhang-gh]

Related #645.

[cheng-kang]

There is a PR for upgrading Marked. Hopefully we'll merge that one soon.