Issue #2552175 by nlisgo, Wim Leers: Follow-up for #2398463: Bartik is telling CKEditor to load a CSS file that no longer exists

Issue #2552187 by Wim Leers, LewisNyman: Follow-up for #2395853: CKEditor is loading system.modules.css, which no longer exists

Issue #2510138 by Wim Leers, droplet, Kingdutch, nod_: Unidirectional editor configuration -> filter settings syncing breaks when button name does not equal the command name

Issue #2304461 by dawehner, neclimdul, naveenvalecha, jibran, tim.plunkett, phenaproxima, Xano, hussainweb, sun, hitesh-jain, amateescu, alexpott, daffie, Mile23, Wim Leers, larowlan: KernelTestBaseTNG™

Issue #2521906 by mErilainen, LewisNyman, Bojhan, eliza411, ivanstegic, lunk_rat, nickrosencrans, stpaultim, Mark LaCroix, webchick: Add default configuration to support h2-h6 level headings

Issue #2501711 by cwells, alexpott: Remove or document SafeMarkup::set in template_preprocess_ckeditor_settings_toolbar

Issue #1392754 by tss, justAChris, jhodgdon: Comply with new documentation standards for @file for namespaced class files

Issue #2511472 by Wim Leers, Fabianx, dawehner: Refactor all usages of drupal_render()/Renderer::render() that break #2450993

Issue #1305882 by dawehner, nod_, Fabianx, Steven Jones, sun, nlisgo: drupal_html_id() considered harmful; remove ajax_html_ids to use GET (not POST) AJAX requests

Issue #2478483 by Wim Leers, Fabianx: Introduce placeholders (#lazy_builder) to replace #post_render_cache

Issue #2383871 by mgifford, rpayanm, a_thakur, maximpodorov, AohRveTPV, jhodgdon: Spellchecking Drupal - PHP

Issue #2491155 by mikeburrelljr, Mac_Weber, opdavies: Update drupal.org and kernel.org URLs in core modules (Follow-up to 2489912)

Issue #1533366 by nod_, valthebald, Jelle_S, Wim Leers: Simplify and optimize Drupal.ajax() instantiation and implementation

Issue #2472323 by dawehner, neclimdul, Crell, kim.pepper, nod_, Wim Leers, larowlan, jibran, pwolanin, catch: Move modal / dialog to query parameters

Issue #2383865 by mgifford, pguillard, rpayanm, alexpott, jhodgdon: Spellchecking Drupal - Javascript

Issue #1081266 by stefan.r, mikeytown2, jeroen.b, tsphethean, mfb, joseph.olstad, marcelovani: Avoid re-scanning module directory when a filename or a module is missing

Issue #2472669 by keopx, rpayanm, rteijeiro, jhodgdon: Complete documentation for every implementation of hook_ENTITY_TYPE_*

Issue #2362637 by yched, slashrsm, rpayanm: Editor.js attach/detach doesn't pass context all the way down

Issue #2470617 by trboslav, MathieuSpil, Manjit.Singh, _nolocation, LewisNyman, YesCT: Clean up css in ckeditor module

Issue #2451665 by dawehner: Don't rebuild the route on ModuleInstaller::install() (30% installer speedup)

Revert "Revert "Issue #2457653 by Gábor Hojtsy: System.site langcode is both used as a file language code and a site language code""

This reverts commit 079a52b4.

Revert "Issue #2457653 by Gábor Hojtsy: System.site langcode is both used as a file language code and a site language code"

This reverts commit 364a6e9c.

Issue #2457653 by Gábor Hojtsy: System.site langcode is both used as a file language code and a site language code

Issue #356399 by dawehner, beejeebus, catch, sidharrell, klausi, nlisgo, Josh Waihi, Berdir, martin107: Optimize the route rebuilding process to rebuild on write

Issue #2442255 by swentel, larowlan, rteijeiro, Wim Leers: Changing text formats on a field makes it impossible to edit

Issue #2329781 by davidhernandez, sidharthap: Move CKEditor toolbar classes from preprocess to templates

Issue #2415855 by emma.maria: A forgotten reference to list.css in Bartik's info file is giving core a 404 error