fix(post): escape swig full tag with args

[stevenjoezhang]

What does it do?

1. For the following content

{% mermaid graph TD %}
A[Hard] -->|Text| B(Round)
B --> C{Decision}
C -->|One| D[Result 1]
C -->|Two| E[Result 2]
{% endmermaid %}

The current state machine implementation will parse {% mermaid graph TD %} and {% endmermaid %} as two separate in-line swig tags (#4780)

2. And according to the static analysis from lgtm, swig_tag_name_begin on line 123 of lib/hexo/post.js is always true
   https://lgtm.com/projects/g/hexojs/hexo?mode=list

Both issues are resolved in this pull request.

How to test

git clone -b swig https://github.com/hexojs/hexo.git
cd hexo
npm install
npm test

Screenshots

Pull request tasks

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

[coveralls]

Coverage increased (+0.001%) to 98.121% when pulling bc32c6c on swig into 902cd70 on master.