Revert "Issue #3405660 by smustgrave, quietone, Wim Leers, larowlan, lauriii: Remove tour from themes"

This reverts commit 3951fa4d.

Issue #3343212 by markconroy, andy-blum, bnjmnm, longwave, alexpott, lauriii, codexmas, harsha012, rpayanm, occupant, Mukeysh, leahtard, joelpittet: Update Core CSS to use double-colon for pseudo elements

Issue #3250357 by mherchel, kostyashupenko, andy-blum, Tim Robinson, Gauravmahlawat: Olivero: Elements within main content that have a high z-index will appear in front of mobile nav

Issue #3051766 by bnjmnm, alexpott, Oleksiy, finnsky, zrpnr, jungle, Wim Leers, vacho, anmolgoyal74, lauriii, tim.plunkett, rachel_norfolk, andypost, catch, Gábor Hojtsy, nod_, fubarhouse: Deprecate and replace jQuery Joyride (for tours)

Issue #2866799 by cwells: Update stylelint rule at-rule-empty-line-before to be consistent with Drupal's CSS standards

Issue #2485293 by MathieuSpil, Manjit.Singh, rudraram, prajaankit, LewisNyman, DeeLay, sqndr: Clean up tour.module.css

Issue #2031641 by aburrows, lauriii, nlisgo, Pol, redsquid, tuutti, LewisNyman, akalata, agviu, kallehauge, _nolocation, rpayanm, saki007ster, mdrummond, RavindraSingh, brahmjeet789: Change active class to is-active

Issue #2027623 by hampercm, larowlan, hussainweb, nick_schuch, droplet, sun, clemens.tolboom: De-fork jQuery Joyride and update to latest stable release

Issue #1921044 by pakmanlh, Manuel Garcia, rteijeiro, dasjo, aboros, sqndr, LewisNyman: Align the styling of tool tips to be more consistent with Seven.

Issue #1938044 by hass, jessebeach, Dragan Eror: Fixed Prefix all toolbar classes to prevent theme clashes.

Issue #1847314 by oresh, jessebeach, mattimck, nod_: Fixed Reduce the dependency on JavaScript for the toolbar to display properly.

Issue #2015789 by fubhy, echoz, rteijeiro, LewisNyman, penyaskito: Remove language_css_alter() (RTL stylesheets) in favor of HTML 'dir' attribute.

Issue #1363112 by mparker17, mgifford, tlattimore, Jacine, dcmouyard, bowersox, ry5n, ahdiaz: Simplify names of 'element-x' helper classes.

Issue #1987066 by Kevin Morse, JohnAlbin, rteijeiro, echoz, ry5n: Rename files to match CSS file naming convention.

Issue #1809352 by nick_schuch, larowlan, jthorson, Wim Leers, Devin Carlson, effulgentsia, tim.plunkett, jessebeach | cweagans: Added Write tour.module and add it to core.