allow markdown.config in config.yml fix #326

[neumayr]

• allow setup of markdown.config in config.yml

markdown.config is a String and not evaluated as a function if you use config.yml

# .vuepress/config.yml
title: Awesome docs
description: Vuepress rocks
markdown:
  lineNumbers: true
  config: |
    md => {
      md.use(require('markdown-it-checkbox'))
      md.use(require('markdown-it-ins'))
      md.use(require('markdown-it-mark'))
    }

🔗 #326

/cc @luminarious

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Summary

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Docs
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• No

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The PR fulfills these requirements:

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Other information:

We aren't ecmascript pros. And we know eval is evil in some context. But we had no better idea…

[ulivz]

Thanks for your work. but we don't think we should support for that.

As you can imagine, when the user does not give config a valid JavaScript string, this will give an error.

So if you need anything JavaScript, please use JS. thanks.

[neumayr]

@ulivz Is there a way to do further checks about this. For example, if the config format is .yml.
Imho, reporting an error is 10x better than not supporting this feature for a supported config format.

Another idea is to allow a config.js and config.yml get merged. So doing the required markdown.config in the JS file.
Or adding a markdown.plugins outlet for specifying plugins as an array.