fix: post_link behaviour when using subdir

[leafbird]

What does it do?

When subdir is used, the generated URL ignores it, creating an incorrect link. If the value of config.url does not end with '/', this was added to create a correct link.

fix #5383

Screenshots

Pull request tasks

• Add test cases for the changes.
• Passed the CI test.

[github-actions]

How to test

git clone -b master https://github.com/leafbird/hexo.git
cd hexo
npm install
npm test

[coveralls]

Pull Request Test Coverage Report for Build 7861542090

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 7 of 7 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 99.53%

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Totals
Change from base Build 7691789796:	0.0%
Covered Lines:	9318
Relevant Lines:	9362

---

💛 - Coveralls

[github-actions]

flamegraph

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