feat: automatically detect dark theme

feat: add loading animation

feat: add table css,fixegoist#13

fix(style): task list

fix(style): don't use fixed height for toc item

fix: add base option and use it as title link

fix: set root to empty string

fix: change scroll position when heading is visible

fix: use throttle instead of debounce,closesegoist#17

chore: fix typo in docs (egoist#15)- Change "Hightlight" to "Highlight"