feat: bind hexo context to helper function callback

[dimaslanjaka]

What does it do?

• Apply hexo context for this callback, useful for plugin written with typescript. Sample
• Fix some missmatch type (fail compile fixed)

Screenshots

based on https://hexo.io/api/helper#How-do-I-use-another-registered-helper-in-my-custom-helper

Pull request tasks

• [ ] Add test cases for the changes.
• [x] Passed the CI test.

[github-actions[bot]]

How to test

git clone -b fix-helper-context https://github.com/dimaslanjaka/hexo.git
cd hexo
npm install
npm test

[dimaslanjaka]

@uiolee @SukkaW review pls, any miss/wrong ?