@vuepress/markdown: migrate to newer version of markdown-it

[DaanDL]

Feature request

I received a message from or audit stating that there's a vulnerability breach in on of our packages through vuepress/markdown -> markdown-it

What problem does this feature solve?

Fixes a vulnerability in markdown-it.

How should this be implemented in your opinion?

The markdown-it depdendency should be updated to at least 12.3.2.

Are you willing to work on this yourself?

Yes