feat(RTL): implement RTL

Using RTLCSS directives, renaming things to use logical names and following best practices.

scss/_card.scss

@@ -69,7 +69,7 @@
   }
 
   + .card-link {
-    margin-left: $card-spacer-x;
+    margin-left: $card-spacer-x #{"/* rtl:ignore */"};
   }
 }
 
@@ -181,7 +181,7 @@
       // Handle rounded corners
       @if $enable-rounded {
         &:not(:last-child) {
-          @include border-right-radius(0);
+          @include border-end-radius(0);
 
           .card-img-top,
           .card-header {
@@ -196,7 +196,7 @@
         }
 
         &:not(:first-child) {
-          @include border-left-radius(0);
+          @include border-start-radius(0);
 
           .card-img-top,
           .card-header {