Let the bookmark support the CDN

[tsanie]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines.
• Tests for the changes have been added (for bug fixes / features).
  • Muse | Mist have been tested.
  • Pisces | Gemini have been tested.
• Docs have been added / updated (for bug fixes / features).

PR Type

What kind of change does this PR introduce?

• Bugfix.
• Feature.
• Code style update (formatting, local variables).
• Refactoring (no functional changes, no api changes).
• Build related changes.
• CI related changes.
• Documentation content changes.
• Other... Please describe:

What is the current behavior?

Issue Number(s): N/A

What is the new behavior?

There is no need to clone the bookmark repo into the source/lib, just set the CDN url instead.

• Screens with this changes: N/A
• Link to demo site with this changes: https://tsanie.us (removed the source/lib/bookmark directory)

How to use?

In NexT _config.yml:

vendors:
  ...
  # use a CDN instead of clone the whole third-party repo
  bookmark: https://cdn.jsdelivr.net/gh/theme-next/theme-next-bookmark@1.0.0/bookmark.min.js

Does this PR introduce a breaking change?

• Yes.
• No.