perf: faster externalLink regexp

[D-Sketon]

What does it do?

Screenshots

Pull request tasks

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

[github-actions]

How to test

git clone -b perf/8.0.0-9 https://github.com/D-Sketon/hexo.git
cd hexo
npm install
npm test

[coveralls]

Pull Request Test Coverage Report for Build 18782178730

Details

• 2 of 2 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 99.526%

---

Totals
Change from base Build 18782167202:	0.0%
Covered Lines:	9866
Relevant Lines:	9913

---

💛 - Coveralls

[stevenjoezhang]

Find another bug: rel.includes('noopenner') should be rel.includes('noopener')
#5729