support async function exported in vuepress config

[dz85]

Before submitting the PR, please make sure you do the following

• [x] Read the Contributing Guidelines.
• [x] Provide a description in this PR that addresses what the PR is solving. If this PR is going to solve an existing issue, please reference the issue (e.g. close #123).

What is the purpose of this pull request?

• [ ] Bug fix
• [x] New feature
• [x] Documentation update
• [ ] Other

Description

support both function form and async function form when using vuepress config file with both vuepress dev and vuepress build.

more about this:

• https://github.com/vuejs/vuepress/pull/1925
• https://github.com/vuejs/vuepress/issues/1185

Screenshots

Before

After

[Mister-Hope]

Can't you write top level await directly? E.g.:

const options = await getOptions()

export default options

So what does your pr actually solves?

[meteorlxy]

Closing per this