allow simple markdown plugin loading

[neumayr]

Feature request

What problem does this feature solve?

markdown.config currently requires a javascript function argument. This is only manageable with a config.js setup. I would like to allow markdown plugin loading also from a config.yml file.
Similar requests, see #326 & #579

What does the proposed API look like?

I would propose a markdown.plugins endpoint that requires an Array. See implementation example.

How should this be implemented in your opinion?

# .vuepress/config.yml
markdown:
  lineNumbers: true
  plugins:
    - ins
    - markdown-it-mark

// .vuepress/config.js
module.exports = {
  markdown: {
    lineNumbers: true,
    plugins: ['ins', 'markdown-it-mark']
  }
}

// vuepress/lib/markdown/index.js:58

  // apply user plugins
  if (markdown.plugins) {
    markdown.plugins.forEach(function (plugin) {
      plugin = plugin.replace('markdown-it-', '')
      md.use(require(`markdown-it-${plugin}`))
    })
  }

Are you willing to work on this yourself?

Yes 🎉 wip branch is alive

[ulivz]

Thanks, It would be better to also support shortcuts without markdown-it-:

module.exports = {
  markdown: {
    lineNumbers: true,
    plugins: ['ins', 'mark']
  }
}

[neumayr]

@ulivz Do all markdown-it plugins have this convention about naming? If yes, I could add a fixed prefix to the require statement. No problem. If you want to support both versions (with and w/o prefix) I'll have to do some string s&r. Is this ok for you?

Check https://github.com/neumayr/vuepress/commit/6be77173bbd7afd0a52adebd29b97a7e506bf74c

[ulivz]

We should support both versions since VuePress's plugin API (In branch) has supported it.

Feel free to open a pull request.

[neumayr]

@ulivz Because a lot has changed with the new v1.0.0-alpha progress.
Is the initial idea still ok, or is there a better integration concept (automatically fetching missing markdown-plugins) like it's done with vuepress plugins…

rebased: d674424