AO3: Tag Hider

Hide tags when there are too many tags automatically on AO3.
Add hide/show tags button to browsing page and reading page.

// Config
const MAX_TAGS_ON_BROWSING_PAGE = 15;
// When number_of_tags > 15, hide tags automatically on browsing page.
// if MAX_TAGS_ON_BROWSING_PAGE = 0, hide tags always on browsing page.

const MAX_TAGS_ON_READING_PAGE = 15;
// When number_of_tags > 15, hide tags automatically on reading page.
// if MAX_TAGS_ON_READING_PAGE = 0, hide tags always on browsing page.

// number_of_tags on reading page also include Rating, Archive Warning, Category and Fandom tags.