Issue #2591827 by longwave, neclimdul, elachlan, daffie: Add YAML linting to core coding standards checks

Issue #3191692 by mherchel, Gauravmahlawat, BhumikaVarshney, bnjmnm, katannshaw: Have secondary menus close on blur

Issue #3108402 by lauriii, bnjmnm, FezVrasta, Wim Leers, mradcliffe, gisle: Update to Popper.js to 2.0.0

Issue #2974553 by Mixologic, justafish, drpal, dawehner: Nightwatch testing fails to save console logs for some tests

Issue #2869825 by justafish, dawehner, alexpott, martin107, jibran, Lendude, Mixologic, michielnugter, droplet, drpal, lauriii, effulgentsia, mglaman: Leverage JS for JS testing (using nightwatch)

Issue #2889600 by droplet, drpal, Gábor Hojtsy, effulgentsia, Wim Leers: [regression] Restore \LocaleJavascriptTranslationTest test coverage and keep testing processed JS file

Issue #2815077 by drpal, mradcliffe, effulgentsia, mpdonadio, nod_, droplet, alexpott, nedjo, tizzo, David_Rothstein, pfrenssen: Adopt airbnb javascript style guide v13 as new baseline javascript coding standards for Drupal 8 core and contrib