Update bootstrap

_sass/bootstrap/_reboot.scss

@@ -54,12 +54,16 @@ body {
   background-color: $body-bg; // 2
 }
 
-// Suppress the focus outline on elements that cannot be accessed via keyboard.
-// This prevents an unwanted focus outline from appearing around elements that
-// might still respond to pointer events.
+// Future-proof rule: in browsers that support :focus-visible, suppress the focus outline
+// on elements that programmatically receive focus but wouldn't normally show a visible
+// focus outline. In general, this would mean that the outline is only applied if the
+// interaction that led to the element receiving programmatic focus was a keyboard interaction,
+// or the browser has somehow determined that the user is primarily a keyboard user and/or
+// wants focus outlines to always be presented.
 //
-// Credit: https://github.com/suitcss/base
-[tabindex="-1"]:focus {
+// See https://developer.mozilla.org/en-US/docs/Web/CSS/:focus-visible
+// and https://developer.paciellogroup.com/blog/2018/03/focus-visible-and-backwards-compatibility/
+[tabindex="-1"]:focus:not(:focus-visible) {
   outline: 0 !important;
 }
 
@@ -184,30 +188,25 @@ a {
   text-decoration: $link-decoration;
   background-color: transparent; // Remove the gray background on active links in IE 10.
 
-  @include hover {
+  @include hover() {
     color: $link-hover-color;
     text-decoration: $link-hover-decoration;
   }
 }
 
-// And undo these styles for placeholder links/named anchors (without href)
-// which have not been made explicitly keyboard-focusable (without tabindex).
+// And undo these styles for placeholder links/named anchors (without href).
 // It would be more straightforward to just use a[href] in previous block, but that
 // causes specificity issues in many other styles that are too complex to fix.
 // See https://github.com/twbs/bootstrap/issues/19402
 
-a:not([href]):not([tabindex]) {
+a:not([href]) {
   color: inherit;
   text-decoration: none;
 
-  @include hover-focus {
+  @include hover() {
     color: inherit;
     text-decoration: none;
   }
-
-  &:focus {
-    outline: 0;
-  }
 }