Increase space between button content and focus border

As noted in w3c/w3c-website#105 (comment)

Author: NicolaSaunders

assets-src/styles/sass/60-advanced-components/_collapsibles.scss

@@ -15,7 +15,7 @@
 		line-height: calc(27 / 18);
 		justify-content: space-between;
 		margin-top: 0;
-		padding: 0;
+		padding: rem(3);
 		width: 100%;
 
 		> span {
@@ -36,6 +36,7 @@
             content: "";
             inline-size: rem(14);
             margin-block-start: rem(4);
+            margin-inline-end: rem(2);
             transform: rotate(45deg);
         }
 

public/dist/assets/styles/advanced.css

@@ -684,7 +684,7 @@ br {
   line-height: 1.5;
   justify-content: space-between;
   margin-top: 0;
-  padding: 0;
+  padding: 0.1875rem;
   width: 100%;
 }
 .js .component--collapsibles [data-heading=collapsibles] button > span {
@@ -703,6 +703,7 @@ br {
   content: "";
   inline-size: 0.875rem;
   margin-block-start: 0.25rem;
+  margin-inline-end: 0.125rem;
   transform: rotate(45deg);
 }
 .js .component--collapsibles [data-heading=collapsibles] button:hover {