Issue #2939940 by bmx269, joelpittet: Update stylelint rules color-hex-case to be consistent with Drupal's CSS standards

Issue #2396489 by herom, rachel_norfolk, WigglyKoala, emma.maria, vijaycs85, jjcarrion: Add missing RTL rules to Bartik theme CSS

Issue #2375673 by DickJohnson, LewisNyman, lauriii, emma.maria, sqndr, Wim Leers, stephr: Split Bartik's CSS into SMACSS style components

Issue #2027181 by Wim Leers, seutje, Bojhan: Use a CKEditor Widget to create a stellar UX for captioning and aligning images.