feat($theme-default): external links in prev/next (close #1962)

[haoranpb]

Summary

fix #1962

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

• Bugfix
• Feature
• Code style update
• Refactor
• Docs
• Build-related changes
• Other, please describe:

If changing the UI of default theme, please provide the before/after screenshot:

Does this PR introduce a breaking change? (check one)

• Yes
• No

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The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)

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• A convincing reason for adding this feature
• Related documents have been updated
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To avoid wasting your time, it's best to open a feature request issue first and wait for approval before working on it.

Other information:

[kefranabg]

Thanks @ludanxer, just a few changes to make and it will be ok

[haoranpb]

Hi @kefranabg ,

Thanks for your tips, really learned a lot since I participated in Vuepress.

When it is an external link, prev.title and next.title will always be undifne, that's why I remove them in the initial PR. Do you think adding prevTitle and nextTitle in the frontmatter would be a good idea?

[kefranabg]

@ludanxer I just made a test and next.title is not undefined if you override the external link name in the config

For example:

[
    'cli',
    'node',
    ['https://vuepress.vuejs.org/', 'External link test']
  ]

[haoranpb]

Oh, right! Sorry, forget to take this scenario into consideration.

[ulivz]

@meteorlxy Could you help review again?

BTW, I felt that it's difficult to maintain continuously since we don't have unit tests for UI components.

[meteorlxy]

What about adding a <OutboundLink /> ?

[haoranpb]

@meteorlxy Thanks for the review.

I didn't add OutboundLink at first because it doesn't look so great.

But you are right, they need to be consistent.

[vue-bot]

Hey @ludanxer, thank you for your time and effort spent on this PR, contributions like yours help make Vue better for everyone. Cheers! 💚

[mbana]

Howdy, is there a version with this available? Many thanks.

[meteorlxy]

@mbana Not yet. It will be available in version 1.3.0

[mbana]

@meteorlxy, I am afraid I can't see that on https://www.npmjs.com/package/vuepress?activeTab=versions.

[meteorlxy]

@mbana

😅 It "will" be. Has not released yet