Issue #2608692 by snehi, r_sharma08, anil280988, marvin_B8, rakesh.gectcr, ashhishhh, malavya, heykarthikwithu, kaushalkishorejaiswal, jhodgdon: Revise docblock for BookManager methods

Issue #2616784 by malcomio, shahinam, r_sharma08, kaushalkishorejaiswal, jhodgdon, cilefen, whatsupdan: Link to render API needs semicolon removed from URL

Issue #2612618 by anil280988, r_sharma08, Cottser, davidhernandez, kaushalkishorejaiswal: Add README.txt file to Stable explain its role as a backwards compatibility layer

(cherry picked from commit d1d0c6e6)

Issue #2604018 by heykarthikwithu, snehi, kaushalkishorejaiswal, pjonckiere: Add @param documentation in __construct() of User module

(cherry picked from commit cbe1e395)

Issue #2606378 by anil280988, kaushalkishorejaiswal, sdstyles: mark \Drupal\Core\Routing\UrlGeneratorInterface::generate() as internal