refactor: use the WHATWG URL API instead of url.resolve

[yoshinorin]

What does it do?

Closes: #4479

We just use new URL. No need to use String.replace() as #4479.

$ node

> new URL("/test", "https://example.com").pathname
'/test'
> new URL("test", "https://example.com").pathname
'/test'
> new URL("test", "https://example.com/").pathname
'/test'
> new URL("/test", "https://example.com/").pathname
'/test'

Screenshots

N/A

Pull request tasks

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

[github-actions]

How to test

git clone -b refactor/use-UL-instead-of-url.resolve https://github.com/yoshinorin/hexo.git
cd hexo
npm install
npm test

[coveralls]

Coverage: 98.733% (-0.0007%) from 98.734% when pulling e03b621 on yoshinorin:refactor/use-UL-instead-of-url.resolve into d485ebd on hexojs:master.