GitHub bring back tabs by regs01

/* ==UserStyle==
@name           GitHub bring back tabs
@namespace      github.com/regs01/usercss
@version        1.2.0
@description    Bringing back tabs, which are far better for readability
@author         coth
@license        MIT
==/UserStyle== */

@-moz-document domain("github.com") {

nav.UnderlineNav
{
  max-width: 1280px !important;
  margin-left: auto !important;
  margin-right: auto !important;
  padding-left: 32px !important;
}

nav.UnderlineNav li
{
  position: relative !important;
  top: 6px !important;
  border-top-left-radius: 4px !important;
  border-top-right-radius: 4px !important;
  overflow: hidden !important;
}

nav.UnderlineNav li > .UnderlineNav-item
{
  border-radius: 0px !important;
  padding-top: 0px !important;
  padding-bottom: 4px !important;
  border-color: transparent;
  border-style: solid !important;
  border-width: 3px 1.5px 0px 1.5px !important;
}

nav.UnderlineNav li > .UnderlineNav-item.selected::after
{
  display: none !important;
}

nav.UnderlineNav li > .UnderlineNav-item.selected
{
  border-top: 3px solid #fd8c73 !important;
  border-bottom: none !important;
}

@media (prefers-color-scheme: light) {
  
  nav.UnderlineNav li > .UnderlineNav-item.selected
  {
    background-color: #fff !important;
    border-left: 1.5px solid #d8dee4 !important;
    border-right: 1.5px solid #d8dee4 !important;
  }
  
}

@media (prefers-color-scheme: dark) {
  
  nav.UnderlineNav li > .UnderlineNav-item.selected
  {
    background-color: #0d1117 !important;
    border-left: 1.5px solid #21262d !important;
    border-right: 1.5px solid #21262d !important;
  }
  
}
  
.gh-header-sticky.is-stuck {
  display: none !important;
}  
  
.gh-header-sticky.is-stuck + .gh-header-shadow {
  display: none !important;
}  
  
.notification-shelf:not(.is-stuck) {
  background: unset !important;
  border: none !important;
}
  
.notification-shelf > .notification-read {
  background: linear-gradient(var(--bgColor-accent-muted), var(--bgColor-accent-muted)) !important;
  padding: 1em 1.2em !important;
  border-radius: 6px !important;
  
}  
  
.notification-shelf.is-stuck {
  background: linear-gradient(var(--bgColor-accent-muted), var(--bgColor-accent-muted)) !important;  
  padding: 0em !important;
}

}