feat(c11n): customize wide screen background (#1313)

* refactor(modal): support offsetLeft when do drawer share

* chore: basic demo done

* chore: more bg pattern pics

* chore(article-viewer): adjust margin

* refactor(drawer): adjust slide out effect for wide screen

* refactor(drawer): some edge case when slide

* refactor(drawer): add upvote for fixedheader when scroll down

* refactor(custom-bg): the switch system done

* refactor(custom-bg): re-org codebase

Author: mydearxym