Issue #3404302 by finnsky, smustgrave, lauriii, markconroy: Create header component for Umami, with JS

Issue #2921133 by quietone, VladimirAus, xjm, ankithashetty, longwave, Prem Suthar, smustgrave, benjifisher, AaronMcHale: Remove "Please" from the codebase

Issue #2632750 by Wim Leers, bnjmnm, krlucas, ronaldtebrake, zaporylie, mherchel, Fabianx, webchick, yogeshchaugule8, catch, darol100, yoroy, Bojhan, Gábor Hojtsy: Interface previews/skeleton screens through optional "preview" or "placeholder" templates

Issue #3278415 by nod_, lauriii, catch, Wim Leers, longwave, xjm, claudiu.cristea: Remove usages of the JavaScript ES6 build step, the build step itself, and associated dev dependencies

Issue #3253148 by mherchel, longwave, ckrina, droplet: Remove IE from core's browserlist, remove non-essential CSS importing and recompile assets

Issue #3174884 by raman.b, alexpott, lauriii, zrpnr, nod_: Update yarn dependencies for Drupal 9.1.0

Issue #3115223 by bnjmnm, lauriii, tedbow, xjm, alexpott: Remove Stable as a base theme of core themes

Issue #3101543 by lauriii, bnjmnm, ravi.shankar, alexpott: Update core JavaScript dependencies listed in package.json

Revert "Issue #3101543 by lauriii, bnjmnm, ravi.shankar: Update core JavaScript dependencies listed in package.json"

This reverts commit 2dadb738.

Issue #3101543 by lauriii, bnjmnm, ravi.shankar: Update core JavaScript dependencies listed in package.json

Issue #2981652 by ApacheEx, corbacho, drpal, dawehner, xjm, alexpott, lauriii: Format core JavaScript using recently add Prettier

Issue #2809635 by markconroy, navneet0693, alexpott, smaz, larowlan, Eli-T, webchick, yoroy, ikit-claw, budda, kjay, timmillwood, tkoleary, Gábor Hojtsy, andrewmacpherson, lauriii, JayKandari, jibran, ok_lyndsey, big_man, ckrina, nathancz, Paul_Gregory, vijaycs85, SharJay, tomphippen, tim.plunkett, Tarun Lewis, cehfisher, kreynen, Petr Illek, mariohernandez, thamas, thatdamnqa, John Cook, philipnorton42, h2cm, kattekrab, martin_q, waako: Create experimental installation profile